Kenai Bluffs Bank Stabilization Section 116 Feasibility Study Kenai, Alaska

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3 Draft Integrated Feasibility Report and Environmental Assessment and Draft Finding of No Significant Impact Kenai Bluffs Bank Stabilization Section 116 Feasibility Study Kenai, Alaska June 2017

4 , and Draft Finding of No Significant Impact Kenai Bluffs Bank Stabilization Section 116 Feasibility Study Kenai, Alaska Prepared by U.S. Army Corps of Engineers Alaska District June 2017

5 DRAFT FINDING OF NO SIGNIFICANT IMPACT In accordance with the National Environmental Policy Act of 1969, as amended, the U.S. Army Corps of Engineers, Alaska District (USACE), has assessed the environmental effects of the following action: Kenai Bluffs Bank Stabilization Section 116 Feasibility Study Kenai, Alaska This project consists of constructing a berm approximately 5,000 feet long below the Kenai Bluffs toe. The project is designed to prevent flood tides from washing away the material that collects at the bluff toe and coastal storms from eroding the lower portion of the bluff. As the material accumulates between the berm and toe of the bluff, the bluff face will be left to erode back naturally to a more stable slope, which is estimated to take up to 15 years. The USACE determined that the project may affect but is not likely to adversely affect species protected under the Endangered Species Act or the Marine Mammals Protection Act, or on essential fish habitat. Under the National Historic Preservation Act, the USACE determined that the project will have no adverse effect on historic properties; the State Historic Preservation Officer has concurred. The environmental assessment supports the conclusion that the coastal storm risk management measures at Kenai, Alaska do not constitute a major Federal action significantly affecting human health and the environment. An environmental impact statement (EIS) is therefore not necessary for this project. Michael S. Brooks Colonel, U.S. Army Commanding Date

6 Executive Summary This General Investigations study was conducted under authority granted by Section 116 of the Energy and Water Development and Related Agencies Appropriations Act of The study seeks to determine the existence of a Federal interest in and the feasibility of constructing coastal storm risk management measures to carry out structural and non-structural projects for storm damage prevention and reduction, coastal erosion, and ice and glacial damage. This study evaluates alternatives to prevent and reduce coastal erosion of approximately 5,000 linear feet of bluff (i.e., Kenai Bluffs) located in the City of Kenai, Alaska. The City of Kenai is 65 air miles and 155 highway miles southwest of Anchorage, Alaska. The local non-federal sponsor (City of Kenai) has stated its intention to cost-share in federally-constructed coastal storm risk management measures in Kenai. The Kenai Bluffs height ranges between 55 to 70 feet and the bluff face is receding at an approximate average rate of 3 feet per year. Public and private property, structures and infrastructure, and cultural resources have been lost and continue to be threatened by the receding bluff. The bluff consists of unconsolidated sediments that remain over steep and unstable because it is exposed to Cook Inlet coastal storms and extreme floodtides that have the fourth largest range in the world of 31.4 feet. Tidal currents and wave action during flood tides attack the toe of the bluff, removing sediments that originate from the bluff face and accumulate at its toe. Coastal storms also degrade the structural integrity of the exposed lower bluff face. In order for the bluff to stabilize, an effective structural project alternative will need to prevent the removal of accumulated sediment at the bluff and the structural damage of the lower bluff. This study evaluates a number of alternatives based on economic, engineering, and environmental and cultural resources factors. In accordance with Section 116 Implementation Guidance, the identification of a Tentatively Selected Plan (TSP) (Alternative 5, Protective Berm) is supported by a Cost Effectiveness/Incremental Cost Analysis (CE/ICA) for the Other Social Effects account, as there is no National Economic Development Plan. While a number of CE/ICA metrics were evaluated and the CE/ICA does inform plan selection, none of the metrics provided enough granularity to choose a plan. Based on additional guidance from USACE Headquarters, the least cost among plans with similar benefits was selected as the most wellreasoned selection criteria. Based on this criteria, the TSP is Alternative 5. The non-federal partner (City of Kenai) supports Alternative 5 as the TSP. Alternative 5 includes constructing a berm at the bluff toe that is designed to prevent the removal of accumulated sediment and prevents damage to the lower portion of the bluff. The bluff surface will be left to erode back naturally to a more stable slope, which is estimated to take up to 15 years. The TSP has a total construction cost with contingency of approximately $32 million (2016 price level). This is referred to as project first cost in the report. The annual investment cost of the project, including the cost of operation and maintenance, is $57,000 with annual National i

7 Economic Development benefits of $846,000. The project s benefits to cost ratio is 0.65 with net annual benefits of negative $463,000. The City of Kenai would be required to pay the non-federal share of 35 percent of the design and construction costs assigned to coastal risk management measures of the project as specified by the Flood Control Act of 1948, as amended, and as specified by the Water Resources Development Act of 1986 (Public Law ), Section 103(c) (4 and 5), as amended. ii

8 Pertinent Data Tentatively Selected Plan Alternative 5: Protective Berm at Toe of Bluff General Berm Feature Units Approximate Amounts Total Length Feet 5,000 Crest Width Range Feet 5.25 to 6.75 Crest Elevation Range Feet above MSL 32.5 to 35 Armor Stone Cubic Yards 42,400 Core Material (B-Rock) Cubic Yards 33,200 Gravel Base 1.5 -inch Cubic Yards 13,100 Filter Fabric / Geotextile Square Feet 225,000 Armor Stone Maintenance / 20 years Cubic Yards 4,200 Item Tentatively Selected Plan Amount Total Estimated Design and Construction Costs (Project First Costs) $32,051,000 Annual Operation and Maintenance $57,000 Total National Economic Development Cost (50 years, 2.875%) $34,488,000 Total National Economic Development Benefits (50 years, 2.875%) $22,300,000 Average Annual Cost $1,309,000 Average Annual Benefits $846,000 Average Net Annual Benefits -$463,000 Benefit to Cost Ratio 0.65 Note: Totals may not sum due to rounding. Conversion Table for SI (Metric) Units Multiply By To Obtain Cubic Yards (cy) Cubic Meters Acre (ac) Hectare Feet Meters Feet Per Second Meters Per Second Inches Centimeters Knots (international) Meters Per Second Miles (U.S. Statute) Kilometers Miles (Nautical) Kilometers Miles Per Hour Kilometers Per Hour Pounds (mass) (lbs) Kilograms Fahrenheit C = (5/9)(F-32) Celsius iii

9 List of Acronyms and Abbreviations ADCRA Alaska Division of Community and Regional Affairs ADEC Alaska Department of Environmental Conservation ADCCED Alaska Department of Commerce, Community, and Economic Development ADFG Alaska Department of Fish and Game ANCSA Alaska Native Claims Settlement Act of 1971 AK Alaska AKDOL&WD Alaska Department of Labor and Workforce Development AWQS Alaska Water Quality Standards AWC Anadromous Waters Catalog C Celsius C-MAN Coastal Marine Automated Network CAA Clean Air Act CEQ Council on Environmental Quality CERCLA Comprehensive Environmental Response, Compensation, and Liability Act CFEC Commercial Fisheries Entry Commission CFR Code of Federal Regulations CIRI Cook Inlet Region, Inc. COL Colonel Corps U.S. Army Corps of Engineers CWA Clean Water Act cy Cubic Yards DPS Distinct Population Segment EFH Essential Fish Habitat EA Environmental Assessment EIS Environmental Impact Statement EPA Environmental Protection Agency ER Engineer Regulations ESA Endangered Species Act EFH Essential Fish Habitat E2USN Estuarine Intertidal Unconsolidated Shore etc. Et Cetera FAA Federal Aviation Administration F Fahrenheit FC Full Compliance FMP Fishery Management Plan FONSI Finding of No Significant Impact FR/EA Feasibility Report and Environmental Assessment FWCA Fish and Wildlife Coordination Act ft feet iv

10 GNF HTRW IDC kg KPB lbs LERR LPP LSF mg MBTA MHHW MHW mph MLLW MLW MMPA MSL MTL N/A NAAQS NED NEPA NHPA NMFS NOAA O&M OCT OMB OMRRR ppt PC PED R S&A SHPO TSP UDV U.S. USACE USC General Navigation Feature Hazardous, Toxic, and Radioactive Wastes Interest During Construction Kilograms Kenai Peninsula Borough Pounds Lands, Easements, Real Estate, and Rights-Of-Way Locally Preferred Plan Local Service Facilities Milligrams Migratory Bird Treaty Act Mean Higher High Water Mean High Water Miles Per Hour Mean Lower Low Water Mean Low Water Marine Mammal Protection Act Mean Sea Level Mean Tide Level Not Applicable National Ambient Air Quality Standards National Economic Development National Environmental Policy Act National Historic Preservation Act National Marine Fisheries Service National Oceanic and Atmospheric Administration Operation and Maintenance Opportunity Cost of Time Office of Management and Budget Operation, Maintenance, Repair, Replacement, and Rehabilitation parts-per-thousand Partial Compliance Preconstruction Engineering and Design Republican Supervision and Administration State Historic Preservation Officer Tentatively Selected Plan Unit Day Value United States U.S. Army Corps of Engineers United States Code v

11 USCG USDA USEPA USFWS USGS USS United States Coast Guard United States Department of Agriculture United States Environmental Protection Agency United States Fish and Wildlife Service United States Geological Survey United States Survey vi

12 Section 116 Feasibility Study - Draft Integrated Feasibility Report and Environmental Assessment Table of Contents 1.0 INTRODUCTION Authority Scope of Study Study Location Congressional District Study Participants/Coordination Non-Federal Sponsor Related Reports and Studies Federal Agencies State Agencies Others PLANNING CRITERIA/PURPOSE AND NEED Problem Statement/Purpose and Need Study Opportunities Objectives National Objectives Study Objectives Study Constraints Criteria National Evaluation Criteria Study Specific Evaluation Criteria BASELINE CONDITIONS/AFFECTED ENVIRONMENT History Demographics Socio-Economics Access to the City of Kenai Government and Tax Structure Kenai Peninsula Borough City of Kenai vii

13 Section 116 Feasibility Study - Draft Integrated Feasibility Report and Environmental Assessment Kenaitze Indian Tribe Cook Inlet Region, Inc. (CIRI) Kenai Natives Association, Incorporated Land Use Physical Environment Climate Topography and Local Drainages Geology Groundwater Occurrence Bathymetry and Oceanography Currents and Tides Waves Ice Conditions Water Quality Air Quality Noise Bluff Erosion Rate Estimate and Mechanisms Erosion Rate Estimate Bluff Erosion Mechanisms Biological Resources Vegetation Fish and Wildlife Protected Species Endangered Species Act Marine Mammal Protection Act Bald and Golden Eagle Protection Act Migratory Bird Treaty Act Special Aquatic Sites and Waters of the United States Essential Fish Habitat Cultural and Historic Resources Subsistence Activities viii

14 Section 116 Feasibility Study - Draft Integrated Feasibility Report and Environmental Assessment 4.0 FUTURE WITHOUT-PROJECT CONDITIONS Economic Conditions Land Damages Structure and Non-Structural Improvement Damages Public Infrastructure Damages Recreation Value Environmental Conditions Climate Change Cultural Resources Political Conditions Summary Without-Project Conditions FORMULATION AND EVALUATION OF ALTERNATIVE PLANS Plan Formulation Rationale Management Measures Criteria and Metrics Structural Measures Non-structural Measures Alternative Descriptions Alternative 1: No Action Alternative 2: River Mouth Relocation Alternative 3: Revetting and Vegetating the Bluff Face- Buried Toe Alternative 4: Revetting and Vegetating the Bluff Face- Weighted Toe Alternative 5: Protective Berm at the Bluff Toe Alternative 6: Structure Relocation Considerations COMPARISON AND SELECTION OF PLANS With-Project Conditions Future With-Project Land Damages Future With-Project Structure Damages Future With-Project Infrastructure Damages Future With-Project Recreation Value ix

15 Section 116 Feasibility Study - Draft Integrated Feasibility Report and Environmental Assessment Summary of Future With-Project Conditions Alternative Plan Costs With-Project Benefits Avoided Land Damages Avoided Structure Damages Avoided Infrastructure Damages Recreation Benefits Net Benefits of Alternative Plans Cost Effectiveness/Incremental Cost Analysis Summary of Accounts and Plan Comparison National Economic Development Regional Economic Development Environmental Quality Other Social Effects Four Accounts Evaluation Summary TENTATIVELY SELECTED PLAN Description of Tentatively Selected Plan Plan Components Plan Costs and Benefits Construction Methodology Financial Analysis Operations, Maintenance, Repair, Replacement, and Rehabilitation (OMRR&R) Avoidance and Minimization Compensatory Mitigation Integration of Environmental Operating Principles Real Estate Conditions Risk and Uncertainty Implementation Schedule Cost Sharing x

16 Section 116 Feasibility Study - Draft Integrated Feasibility Report and Environmental Assessment 9.0 ENVIRONMENTAL CONSEQUENCES Physical Environment Climate Geology River Sediment Transport Bathymetry Ice Conditions Water Quality Air Quality Noise Currents and Tides River Flow Rate Biological Resources Protected Species Endangered Species Act Noise Generation at the Project Site Marine Mammal Protection Act Bald and Golden Eagle Protection Act Migratory Bird Treaty Act Special Aquatic Sites and Waters of the United States Essential Fish Habitat Cultural Resources Archaeological and Historic Structures Coastal Zone Resource Management Environmental Justice and Projection of Children Unavoidable Adverse Impacts Cumulative and Long-term Impacts Comparison of the Effects of the Project Alternatives PUBLIC AND AGENCY INVOLVEMENT Public/Scoping Meetings Federal and State Agency Coordination xi

17 Section 116 Feasibility Study - Draft Integrated Feasibility Report and Environmental Assessment Relationship to Environmental Laws and Compliance Status of Project Coordination Status of Environmental Compliance (Compliance Table) Views of the Sponsor CONCLUSIONS AND RECOMMENDATIONS Conclusions Recommendations REFERENCES List of Tables Table 1. Brief post-contact timeline Table 2. Selected Climate Data, Kenai Municipal Airport ( ) Table 3. Relative Sea Level Rise Prediction Table 4. Tidal Parameters Kenai River Entrance Table 5. Future Without-Project Land Damages Table 6. Future Without-Project Structure and Non-Structural Improvement Damages Table 7. State of Alaska Population Projections for the Kenai Peninsula Borough Table 8. Summary of Future Without-Project Conditions Table 9. Structural Measures Considered Table 10. Non-Structural Measures Table 11. Future With-Project Land Damages Table 12. Future With-Project Structure Damages Table 13. Future With-Project Public Infrastructure Damages Table 14. Future With-Project Recreation Value Table 15. Summary of Future With-Project Conditions Table 16. Total Project Costs by Alternative Table 17. Avoided Land Damages, by Alternative Table 18. Avoided Structure Damages, by Alternative Table 19. Avoided Infrastructure Damages, by Alternative Table 20. Recreation Benefits, by Alternative Table 21. Summary of With-Project Benefits Table 22. Summary of Benefits and Costs, by Alternative Table 23. Cost Effectiveness/Incremental Cost Analysis Criteria Table 24. Four Accounts Evaluation Summary Table 25. General Berm Components Table 26. Summary of Benefits and Costs, by Alternative Table 27. LERDS xii

18 Section 116 Feasibility Study - Draft Integrated Feasibility Report and Environmental Assessment Table 28. Risk and Uncertainty Summary Table 29. Proposed Milestone Schedule Table 30. NOAA Noise Effects Threshold Table 31. Typical Air-Transmitted Noise Levels of Anticipated Project Construction Equipment Table 32. Comparison of the Effects of the Project Alternatives Table 33. Summary of Relevant Federal Statutory Authorities List of Figures Figure 1. Project Location and Study Area... 2 Figure 2. Personal Use Dip-netting Fishery (courtesy: ADFG) Figure 3. Pacific Star Seafoods and Eastern Terminus of the Bluff Figure 4. Plot of Relative Sea Level Rise curves Figure 5. Major Surface Drainages at Project Site Figure 6. Soil and Groundwater Conditions Figure 7. Depths near the Kenai River Mouth (Excerpt from NOAA Chart 16662) Figure 8. Design Waves by Reach Figure 9. Kenai River estuary at the base of the eroding bluff showing highly turbid water Figure 10. Expected Erosion Extent in Figure 11. Erosion Processes Figure 12. Waves during a Storm Event at Kenai Bluffs Figure 13. Trees and Root Balls Failing Figure 14. Photograph dated 2001 showing typical distribution of vegetation along the face and top of the bluff Figure 15. Photograph dated April 2016, showing intertidal zone at a low tide near 0.0 ft. MLLW Figure 16. Longfin Smelt Caught in Kenai River in 2002 (photo courtesy of Tim McKinley/ADFG) Figure 17. Cook Inlet Beluga Whale Habitat Areas (Source: NOAA) Figure 18. Harbor Seal Haul-out Areas Reported in the Kenai River Estuary (in blue) Figure 19. An Annotated National Wetlands Inventory Habitat Map of The Kenai River Estuary, Generated at the NWI Website (USFWS 2016) Figure 20. Kenai River Personal Use Fishery Regulation Areas (adapted from ADFG 2016a).. 43 Figure 21. Plan View of River Mouth Relocation Figure 22. Channel Requiring Maintenance Dredging Figure 23. Alternative 3 Plan View - Revetment with Buried Toe Figure 24. Alternative 3 Typical Section Revetment with Buried Toe Figure 25. Alternative 4 Typical Section Revetment with Weighted Toe Figure 26. Alternative 5 Typical Section Berm at Bluff Toe Figure 27. Cost Effectiveness for Stabilized Bluff Parcels xiii

19 Section 116 Feasibility Study - Draft Integrated Feasibility Report and Environmental Assessment List of Appendices Appendix A 404(b)(1) Evaluation under the Clean Water Act Appendix B Hydraulics and Hydrology Appendix C Economics Appendix D Geotechnical Evaluation Appendix E Cost Engineering Appendix F Real Estate Appendix G Environmental Correspondence xiv

20 1.0 INTRODUCTION 1.1 Authority This General Investigations study was conducted under authority granted by Section 116 of the Energy and Water Development and Related Agencies Appropriations Act of The Secretary of the Army is authorized to carry out structural and non-structural projects for storm damage prevention and reduction, coastal erosion, and ice and glacial damage in Alaska, including relocation of affected communities and construction of replacement facilities: Provided, that the non-federal share of any project carried out pursuant to this section shall be no more than 35 percent of the total cost of the project and shall be subject to the ability of the non-federal interest to pay, as determined in accordance with 33 U.S.C. 2213(m). 1.2 Scope of Study This study evaluates Federal interest in and the feasibility of constructing coastal storm risk management measures, and proposes a Tentatively Selected Plan (TSP) to prevent and reduce the negative effects of the receding Kenai River Bluff, herein referred to as the Kenai Bluffs. This study was conducted and the report prepared in accordance with the goals and procedures for water resource planning as contained in Engineer Regulation (ER) , Planning Guidance Notebook, which defines the contents of feasibility reports for coastal storm risk management projects. ER , Procedures for Implementing NEPA directs the contents of environmental assessments. This document presents the information required by both regulations as an integrated Feasibility Report and Environmental Assessment (FR/EA). It also complies with the requirements of the Council on Environmental Quality regulations for implementing the National Environmental Policy Act of 1969 (42 USC 4341 et seq.). This draft FR/EA documents the analysis and coordination conducted to determine whether the Federal government should participate in constructing coastal storm risk management measures in Kenai, Alaska. Studies of this nature consider a wide range of alternatives and the environmental consequences of those alternatives. A consideration of benefits under authority granted by Section 116 allows the U.S. Army Corps of Engineers, Alaska District (USACE) to identify a recommended plan. 1.3 Study Location The study area is located in the City of Kenai on the western coast of the Kenai Peninsula, 65 air miles and 155 highway miles southwest of Anchorage (Figure 1). The Kenai Bluffs coastal erosion area is approximately 5,000 linear feet of high bank that ranges in height from 55 to 70 feet above the toe along the north bank of the Kenai River at the river mouth to Cook Inlet (Figure 1). Cook Inlet extends 180 miles from the Gulf of Alaska to Anchorage in Southcentral Alaska. 1

21 Figure 1. Project Location and Study Area 1.4 Congressional District The study area is in the Alaska Congressional District, which has the following congressional representation: Senator Lisa Murkowski (R-AK) Senator Dan Sullivan (R-AK) Representative Don Young (R-AK) 1.5 Study Participants/Coordination The USACE is the lead agency for this coastal storm risk management General Investigations study. The studies that provide the basis for this report were conducted with the assistance of many individuals and agencies, including: The City of Kenai, the U.S. Fish and Wildlife Service (USFWS), the U.S. Coast Guard (USCG), the State of Alaska Department of Fish and Game (ADFG), the State of Alaska Department of Environmental Conservation (ADEC), Alaska Department of Commerce, Community, and Economic Development (ADCCED), Alaska Department of Labor and Workforce Development (AKDOL), the National Marine Fisheries 2

22 Service (NMFS), and many members of the interested public who contributed information and constructive criticism to improve the quality of this report. 1.6 Non-Federal Sponsor The City of Kenai is the non-federal sponsor and has stated its intention to cost-share in federally-constructed coastal risk management measures. The Federal Cost Sharing Agreement (FCSA) for this Study was signed May 12, This agreement creates a Federal and non- Federal partnership with the objective to effectively serve both local and national interests. 1.7 Related Reports and Studies According to the City of Kenai (Koch 2015), the receding bluff has affected residents of the community for 100 years. The USACE has been involved in various studies of the Kenai River since at least 1962 when the U.S. Army Engineer District, Alaska, Foundations and Materials Branch (USACE 1962) evaluated rip rap source materials for navigation improvement projects, and later navigability improvement studies of the Kenai River (USACE 1970 and 1976). With respect to the bluff erosion issue specifically, The City of Kenai commissioned a study in 1982 (TAMS 1982), with the USACE intermittently involved since at least 1997 when the USACE published a reconnaissance report that investigated navigation improvements and erosion control on the Lower Kenai River (USACE 1997). The Energy and Water Development Appropriations Act of 2002, Senate Report authorized the Corps to expend up to $500,000 to conduct a special technical evaluation of bank stabilization needs along the lower Kenai River. Due to this previous Congressionally-directed work, significant technical analyses have been completed regarding Kenai Bluffs erosion. Existing analyses from this work include technical reports related to the following: geotechnical and hydraulic conditions, preliminary environmental analysis, cultural and historic resources, real estate in the affected area, groundwater conditions, a revetment design, and the construction cost of that design. Various Kenai Bluffs erosion studies completed by Federal and state agencies and others are listed chronologically below, with brief annotations about the report content: USACE Reconnaissance Report, Kenai River, Alaska, U.S. Army Corps of Engineers, Alaska District, November This report performed a reconnaissance level evaluation of providing flood risk management measures along the Kenai River. A Federal interest could not be justified. USACE Feasibility Study, Kenai Harbor, Alaska, Small Boat Harbor and Deep-Draft Navigation Improvements, U.S. Army Corps of Engineers, Alaska District, February This study could not establish a Federal interest in constructing navigation improvements in Kenai at this time. 3

23 USACE Kenai River Review, Final, U.S. Army Corps of Engineers, Alaska District, April This review is akin to a modern day watershed study. It detailed navigable reaches of the river, ownership of the river bottom, riparian rights, Federal jurisdiction, ordinary high water marks, and water rights. It also performed some analysis of environmental conditions related to the area s biology, geology, hydrology, and socio-economics. USGS Erosion and Sedimentation in the Kenai River, Alaska, U.S. Geological Survey, This report presented an assessment of erosion and sedimentation of the entire Kenai River. USACE Reconnaissance Report for Navigation Improvements and Erosion Control, U.S. Army Corps of Engineers, Alaska District, June This report established a Federal interest in participating in a cost-shared feasibility study of coastal erosion at the mouth of the Kenai River. USACE. 2004a. Geotechnical Findings Report, Kenai River Bluff Erosion, Kenai, Alaska, U.S. Army Corps of Engineers, Alaska District, October This report provided a summary of findings based on site observations and results of field exploration, laboratory testing, and engineering computations. USACE Kenai River Bank Erosion Technical Report, Kenai Alaska, U.S. Army Corps of Engineers, Alaska District, May As directed by the Energy and Water Development Appropriations Act of 2002, Senate Report , this report assessed environmental resources at the lower Kenai River, identified the mechanisms for bluff erosion, and assessed environmental and hydrogeomorphic consequences of bluff stabilization. USACE Geotechnical Investigation and Site Conditions Report, Kenai River Bluff Erosion, U.S. Army Corps of Engineers, Alaska District, February This report documents sediment sampling and test borings for the study area along with a thorough geotechnical assessment; performed by R&M Consultants, Inc. See Appendix D. USACE. 2008a. Groundwater Monitoring Report, Kenai River Bluff Erosion, U.S. Army Corps of Engineers, Alaska District, January This report documents groundwater monitoring activities performed by R&M Consultants, Inc. See Appendix D. USACE. 2008b. Kenai River Bluff Erosion, Bluff Stabilization Design Alternatives, Design Alternatives Report, U.S. Army Corps of Engineers, Alaska District, October 2008, prepared by Tetra Tech. This report provides the design of bluff stabilization along with detailed engineering drawings for the preliminary design. 4

24 USACE. 2009a. Kenai River Bluff Erosion, Bluff Stabilization Design Alternatives, Draft Design Report, U.S. Army Corps of Engineers, Alaska District, March 2009, prepared by Tetra Tech. This report provides the design of bluff stabilization along with detailed engineering drawings for the preliminary design. USACE Kenai River Bluff Limited Economic, Cultural and Historic Property Evaluation, Draft, U.S. Army Corps of Engineers, Alaska District, December This report documents an evaluation of lost income and diminished opportunities of businesses along the bluff as they are forced to relocate because of ongoing erosion, as well as potential losses of historical and cultural sites; prepared by Tetra Tech. USACE Kenai River Bluff Stabilization, Kenai, Alaska, Cost Engineering Report Draft Submittal, U.S. Army Corps of Engineers, Alaska District, June This report contains detailed cost estimates of the construction features presented in the Design Alternatives Report dated June 2011; performed by Tetra Tech. USACE Kenai River Bluff Erosion Section 905(B) (WRDA) Analysis. University of Alaska Anchorage (UAA) Erosion at the Mouth of the Kenai River, Alaska April 2001, University of Alaska Anchorage, Orson Smith, William Lee, and Heike Merkel. Report contains a sediment budget analysis with regard to the proposed Kenai Coastal Trail and Erosion Control Project, PND, February ADF&G Estimates of Chinook Salmon Abundance in the Kenai River Using Split-Beam Sonar, State of Alaska Department of Fish and Game, December This report provided data on abundance of Chinook salmon (Oncorhynchus tshawytscha) in the Kenai River. Tippetts-Abbett-McCarthy-Stratton (TAMS) City of Kenai River Bluff Erosion Study, Draft Report, November This report was commissioned by the City of Kenai to investigate the regression of the high bluff referred to as the Kenai River Bluff and to recommend remedial measures. Peratrovich, Nottingham, and Drage, Inc. (PND) 2000 and Kenai Coastal Trail and Erosion Control Project, Design Concept Report, January 2000 and February 2002 reports. These reports provide a design concept of bluff stabilization and a pedestrian trail along the bluff. 2.0 PLANNING CRITERIA/PURPOSE AND NEED 2.1 Problem Statement/Purpose and Need The coastal erosion at the mouth of the Kenai River results in over-steepening, collapse, and inland retreat of the Kenai Bluffs. This ongoing condition negatively impacts and continues to 5

25 threaten commercial, municipal, and private property (land, structures, and infrastructure), as well as cultural and historical resources in Kenai, Alaska. The purpose of this study is to determine the feasibility of constructing erosion control measures that prevent and/or reduce the effects of bluff erosion over the 50-year period of analysis, particularly damages to structures, infrastructure, and cultural and historical resources. The ongoing condition of the receding Kenai Bluffs has resulted in: Lost land to the sea: commercial, municipal, non-profit (e.g., Kenai Bible Church built in 1940): o 7 parcels have been completely lost o 18 parcels have suffered land loss o Nearly all threatened parcels have lost value Lost and damaged cultural resources (i.e., historical, potentially historical, and archeological sites): o 4 historic wooden structures o Historic property of Kenai Bible Church o Human remains have eroded out of the bluff o Prehistoric house depressions have been lost or are exposed Abandoned and/or condemned structures: residential, commercial, and municipal Threatened structures and infrastructure: residential, commercial, non-profit, and municipal (e.g., Kenai Senior Center) Relocation of utilities and roads In addition, the ongoing receding Kenai Bluffs has had other negative impacts (i.e., other social effects) as listed below: Cultural vulnerability with local tribes and the local population Under use of public-use areas by locals and tourists (e.g., scenic overlooks and nearby parks) Health and safety issues (The unstable bluff is preventing activities at the base and near the top edge of the bluff, although high pore pressures causing soft sediments on the beach area may continue to prevent activities at the base.) Negatively impacted social connectedness, identity, resiliency, leisure, and recreation Contributes to uncertainty in community planning 2.2 Study Opportunities Study opportunities are statements about things that will or have the potential to be realized by meeting the main study objectives. The study opportunities that could be realized with a stabilized bluff include: 6

26 Prevented or reduced damages or loss of property, structures, and cultural resources Managed risks associated with bluff erosion Enhanced stable environment with a stable streambank and riparian corridor Improved recreational usage of the area Enhanced navigation consistent with ER , Appendix E, Section II, E-8, b. (7) The exceptional water front view from the top of the bluff encourages tourism and, if the bluff were stable, it would also: Enhance the economic values of property and assets Encourage development of the area Increase the tax base value of the area 2.3 Objectives The Federal objective of water and land resources planning is to contribute to National Economic Development (NED) in a manner consistent with protecting the nation s environment. NED features increase the net value of goods and services provided to the economy of the nation as a whole. Generally, only benefits contributing to NED may be claimed for Federal economic justification of a project. However, if there is no NED plan, Section 116 Implementation Guidance allows for selection of a plan based in part or whole on non-monetary units supported by a Cost Effectiveness/Incremental Cost Analysis (CE/ICA). This study s general objective is to propose an erosion control measure or combination of measures as a TSP that prevents and reduces the negative effects of bluff erosion, particularly damages to structures, infrastructure, and cultural resources caused by the receding Kenai Bluffs over the 50-year period of analysis. 2.4 Study Constraints Study constraints are statements about what you want to avoid doing, or things you cannot change, while meeting your objectives. Due the physical location of the Kenai Bluffs at mouth of the Kenai River, physical construction of any project will pose challenges associated with a reduced construction season due to winter conditions, tidal schedules, potential coastal storms, seasonal commercial fishing fleet, and sport fishing boat traffic. Study constraints primarily involve the engineering, economic, and environmental criteria items that are discussed in the report sections that follow. Study constraints include: Any enacted solution must consider all natural processes that are significantly contributing to bluff erosion including: waves, tides, ground water seepage, and overbank flow. 7

27 Plans must minimize adverse impacts to navigation. Plans must minimize adverse impacts to fisheries. Plans must avoid or minimize impacts to historic sites and/or critical infrastructure. 2.5 Criteria Alternative plans should be formulated to address study objectives and adhere to study criteria. Each alternative plan shall be formulated in consideration of four criteria: completeness, efficiency, effectiveness, and acceptability. Completeness is the extent to which alternative plans provide and account for all necessary investments or other actions to ensure the realization of the planning objectives, including actions by other Federal and non-federal entities. Effectiveness is the extent to which alternative plans contribute to achieve the planning objectives. Efficiency is the extent to which an alternative plan is the most cost-effective means of achieving the objectives. Acceptability is the extent to which alternative plans are acceptable in terms of applicable laws, regulations, and public policies. Mitigation of adverse effects shall be an integral component of each alternative plan. For the NED analysis, average annual costs are compared to average annual benefits expected to be derived from each alternative evaluated. Applying an appropriate discount rate and period of analysis makes costs and benefits comparable on the equivalent time value of money. For this analysis, the Federal fiscal year 2017 discount of percent is used, as well as a 50-year period of analysis. Each alternative has a total construction cost estimate, or project first cost, prepared by Cost Engineering utilizing MCASES. The total economic (NED) cost used in the NED analysis is the sum of project first costs, interest during construction, and operation and maintenance expenses. Further discussion of the NED analysis can be found in the Economics Appendix. The TSP that effectively serves both Federal and non-federal interest must be designed and constructed so that it safely and efficiently meets the main objective of preventing and reducing the damages to structures, infrastructure, and cultural and historical resources caused by the receding Kenai Bluffs over the 50-year period of analysis. The following goals and objectives, based on the needs described in Section 2.3, are related to providing an erosion control measure that is safe, usable, and maintainable. 8

28 Constructability: Constructability is defined by the following question: Do site-specific conditions cause the measure to be technically infeasible or not applicable as a storm damage risk management measure? The associated metric is Yes/No. Constraint Avoidance: Constraint avoidance is defined as a measure s ability to avoid study constraints. The associated metric is Yes/No. Social Considerations: Social Considerations is defined as The extent to which a measure is judged to be acceptable to agencies, tribes, and the general public. This also includes or captures other social effects (OSE). The associated metric is High/Medium/Low. 3.0 BASELINE CONDITIONS/AFFECTED ENVIRONMENT 3.1 History Kenai and the surrounding area has been used extensively by Dena ina Athabascan people in general and the Kahtnuht ana Dena ina people of the Kenaitze tribe in particular for generations. The Dena ina name for the Kenai River mouth is Kahtnu Kaq (Trefon et al. 2014). A brief post-contact timeline is summarized in Table 1. 9

29 Table 1. Brief post-contact timeline Year Historical Activity 1741 Russian fur traders arrive at the Athabascan village of Shk ituk t which has a population of about 1, The Russians construct the second permanent Russian settlement in Alaska at Fort St. Nicholas, a fortified fur and fish trading post The Russian American Company builds a Russian Orthodox Church at Kenai The U.S. purchases Alaska from Russia The U.S. Military constructs Fort Kenay, a post for Dena ina people in the area The first commercial salmon cannery, the Northern Packing company, opens in Kenai The first U.S. Post Office is constructed in Kenai Homesteading enables the area to develop A dirt road connects Kenai to Anchorage Oil is discovered at Swanson River, 20 miles northeast of Kenai. It is the first major oil discovery in Alaska The City of Kenai is incorporated The discovery of oil in Cook Inlet brings in a period of accelerated growth. 3.2 Demographics The City of Kenai had a population of 7,100 according to the 2010 census, up 2.3 percent from 6,942 at the 2000 census. In 2014 the State of Alaska Department of Labor and Workforce Development (AKDOL&WD) estimated the City of Kenai population to be 7,167. After rapid increases during the economic booms of the 1960 s through the 1980 s, population growth in Kenai began to stabilize by 2000, with more long-term residents and a generally older population. Several other communities, such as Soldotna, Nikiski, Kasilof, and Sterling, are within 20 miles of Kenai, giving the northwest Kenai Peninsula a population of roughly 34,000. The racial makeup of the Kenai population in 2010 was about 80 percent white, 14 percent Alaska Native or American Indian, and 6 percent Asian, other races, or multi-racial. The proportion of people living below the poverty line was 9.4 percent (ADCRA 2016). 3.3 Socio-Economics The City of Kenai is the commercial and service center for the western Kenai Peninsula and a local center of government. It has a per capita income of $31,700 and a median household income of $63,000. Approximately 9 percent of residents fall below the Federal poverty level. 10

30 The Kenai area has a substantial industrial economy, built largely on petroleum and fishery resources. Fisheries are a large part of Kenai s economy. The city s largest employers are the Kenai Peninsula Borough (KPB) school district, Unocal, Peak Oilfield Services, the borough government, and the Central Peninsula General Hospital (City of Kenai 2013, ADCRA 2016). The State of Alaska Division of Community and Regional Affairs (ADCRA 2016) reported that in 2014, 282 separate commercial fishing permits were issued and that fisheries provided over $10 million in earnings. Significant economic activity is also associated with subsistence, sport, and personal use fisheries, particularly during the annual dip-netting opener, which allows Alaska residents to harvest at least 25 salmon per household (Figure 2). Additionally, the Kenai populace provides labor and services to energy exploration and production facilities in nearby Cook Inlet. Figure 2. Personal Use Dip-netting Fishery (courtesy: ADFG) 3.4 Access to the City of Kenai The City of Kenai is accessible by road, air, and water. A paved highway system connects the city to Anchorage and beyond. The Kenai Municipal Airport is located about 1 mile north of the Kenai Bluffs project area. It is served by three full-service commuter airlines and charter services utilizing two runways: a paved 7,500-foot and gravel 2,000-foot runway. Boat access is available via commercial and private facilities on the Kenai River and limited commercial docking facilities along Cook Inlet coast. 11

31 3.5 Government and Tax Structure The City of Kenai is within the KPB. In Alaska, boroughs are equivalent to county-level governments and are responsible for providing a number of services. The KPB is governed by an elected mayor and nine-person Borough Assembly. The KPB currently levies a 3 percent sales tax and a 4.50 mill property tax (ADCRA 2016). The City of Kenai is a Home Rule City that currently levies a 3 percent sales tax and an 8.86 mill property tax. A 5 percent bed tax has been suspended indefinitely. The city is governed by an elected mayor and a six-person City Council. The Kenaitze Indian Tribe, or Sovereign Nation of the Kenaitze, is a federally recognized tribe with 1,600 members. The tribe elects a seven-person Executive Council with members serving 2- year staggered terms. The tribe is active in administering a number of programs including education, housing, environmental services, elder services, youth programs, language resources, and others. The Nitghuk t uch qenashen Tribal Court upholds tribal law. CIRI is one of the 13 regional corporations established by the Alaska Native Claims Settlement Act of 1971 (ANCSA) and holds title to 1.3 million acres of subsurface estate, making it one of Alaska s largest private landowners. These subsurface holdings include lands within the study area along the southern bank of the Kenai River. CIRI is active in many business ventures including energy, infrastructure, construction, real estate, tourism, and other services. Kenai Natives Association, Inc. is the ANCSA village corporation for Kenai. 3.6 Land Use Land divisions along the bluff are generally low density residential with some commercial and park space. Land ownership along the bluff is a mix of private and municipal, and the land is zoned Central Mixed Use, Central Commercial, or Conservation by the City of Kenai (City of Kenai 2013). The land along or adjacent to the bluff features in several city planning proposals, including a revitalized city center and a Millennium Square development making use of the vacant land east of the Senior Citizen s Center (City of Kenai 2013, Tetra Tech 2007). Additional uses include walking, biking, and wildlife viewing. The bluff face itself is too unstable for any current use, but the properties at the top of the bluff include a number of homes, businesses, and facilities expected to be impacted by erosion over the period of analysis. The largest structures within the threatened area are the Kenai Senior Center and Vintage Pointe Independent Senior Housing Facility, both of which are owned and 12

32 operated by the City of Kenai and are valued at approximately $7.9 million. A family practice clinic (Central Peninsula Family Practice), a historic local bar (Kenai Joe s), the Kenai Bible Church, and several vacation rental operations are among the establishments fronting the bluff that would be lost to erosion under the no action alternative. Three of the properties within the 50-year erosion area have been determined as historically significant, with a dozen more being eligible for significance. At the far eastern end of the bluff is the Pacific Star Seafoods processing plant, which falls outside the project area (Figure 3). The project footprint itself is primarily the base of the eroding bluff and the adjacent intertidal zone, an area that sees little public use (Gease 2016, Sinclair 2016). Most of the north shoreline of the estuary, from below Main Street eastward to the city dock, is closed to the popular shorebased salmon dip-net fishery pursued elsewhere along the estuary (ADFG 2016a), due in part to the bluff erosion and the risk of persons being trapped against the steep bluff by a rising tide. Dip-net fishing is allowed along the shore from below Main Street westward, which overlaps the western end of the project area by roughly 500 feet. People occasionally venture onto the intertidal zone below the bluff to angle for fish, bird-watch, or to walk. Pacific Star Seafoods Figure 3. Pacific Star Seafoods and Eastern Terminus of the Bluff 13

33 Two City of Kenai parks are near the project area. Kenai Beach Park (600 South Spruce Street) is opposite Cemetery Creek from the west end of the project area. This park offers mostly access to the beaches to the west of the Cemetery Creek mouth, although the public can access the Kenai River bank east of Cemetery Creek using a footbridge across the creek about 800 feet north of its mouth. Eric Hansen Scout Park (913 Mission Avenue) is on the top of the bluff just northwest of the project s western terminus. The ADFG recommends Eric Hansen Scout Park as a vantage point from which to view birds, seals, and beluga whales using the Kenai River estuary (ADFG 2016b). 3.7 Physical Environment Historical Data The climate along the Cook Inlet coast at Kenai shows a mix of maritime and continental interior influences, with cool summers, cold winters, frequent fog, and relatively sparse precipitation. The inlet has a moderating effect on the local climate, but Kenai s proximity to the Alaska Range to the west and the Kenai Mountains to the east give Kenai slightly cooler average temperatures than seen in Anchorage, 65 miles to the northeast. Kenai temperatures typically average from 4 to 22 F in winter, and 46 to 65 F in the summer (City of Kenai 2013, ADCRA 2016). Table 2 below summarizes climate data from a weather station at the Kenai Municipal Airport, less than a half-mile north of the proposed project site (WRCC 2016). Table 2. Selected Climate Data, Kenai Municipal Airport ( ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec ANNUAL Ave. Max. Temp. ( F) Ave. Min. Temp. ( F) Ave. Total Precip. (in) Ave. Total Snowfall (in) Ave. Snow Depth (in) Prev. Wind Direction NNE NNE NNE N SSW SSW SSW S NNE NNE NNE NNE NNE Ave.Wind Speed (mph) Source: Western Regional Climate Center 2016 Based on wind data available from the Kenai Airport FAA station for the years 1970 through 2015, the predominant wind direction is from the northeast from September to April with an average speed of 7.9 miles per hour and peaks over 20 plus miles per hour. During the summer months of May through August, the dominant wind direction is from the southwest with much less intensity. 14

34 Sea Level Rise The USACE Engineering Regulation (ER) provides guidance for incorporating the effects of projected future sea level change (SLC). The range of possible future rates of change are represented by three scenarios of low, intermediate, and high sea-level change. The SLC low rate is the historic SLC. The intermediate and high rates are computed using National Research Council s (NRC) Curve I, and the modified NRC Curve III and NRC equations (see Appendix B). The NRC results were adjusted to a measured local sea level trend using approximately 40 years of NOAA data published for Nikiski, Alaska, which is about 10 miles from the Kenai Bluffs. The southcentral area of Alaska has been experiencing post-glacial rebound, also called isostatic rebound, with a resultant sea level trend for Nikiski at feet/year. This value was used to adjust the values from the NRC equations with the results presented in Table 3, with the adjusted curves shown in Figure 4. Table 3. Relative Sea Level Rise Prediction Sea Level Change Low Intermediate High Base year (1992) 0.00 feet 0.00 feet 0.00 feet Project start year (2018) feet feet feet 50 years (2068) feet feet feet 100 years (2118) feet feet 1.84 feet 15

35 Figure 4. Plot of Relative Sea Level Rise curves For an assumed construction start in 2018 and a 50-year period of analysis, a project at Kenai could see the relative sea level fall by 1.60 feet or rise by as much as 0.29 feet. In 100 years, the relative sea level could fall by 3.21 feet or rise by 2.43 feet (Table 3). It is unlikely that the sea level would rise as much as predicted under the High scenario since, in general, the southcentral area of Alaska has been experiencing isostatic rebound. For this study the intermediate rate of sea level change was used for calculations since the historic records for the area indicate that the Kenai area is experiencing a relative sea level reduction and not a relative sea level rise. In the unlikely event that High Level of Relative Sea Level Change noted in Table 3 occurs, the design can be adapted to increase the revetment height. The proposed design can be modified by adding armor stone to the revetment crest to prevent wave attack during storm events. The project area is characterized by a modified glacial moraine topography, which is separated by an interlacing pattern of swamps and muskegs developed in abandoned drainage channels and broad depressions. The Kenai River and its tributaries drain an area of 2,148 square miles and flow for a total of 68 river miles from Kenai Lake to Cook Inlet, which has a tidal range as high as 31.4 feet. Tidal levels influence extends to approximately river mile 12 in the Kenai River. 16

36 The Kenai River flow is influenced by glacial melt water with the lowest daily discharges in the winter season and higher discharges occurring in the summer. Historical Kenai River discharge records at Soldotna, near river mile 20, show daily mean discharge can range from of a high of 41,400 cubic feet per second (cfs) and a low of 770 cfs. Discharge is typically between 1,300 and 15,000 cfs, with average discharges in July, August, and September of approximately 13,000 cfs. The north-side Kenai River bank (i.e., Kenai Bluffs) height above the toe ranges from 55 to 70 feet and is exposed to waves and tide levels from Cook Inlet. The opposite south-side bank is a low-lying wetland and tide flat area that experiences less impact from waves originating in Cook Inlet but is flooded significantly during the high tides. Three primary drainages within the project area (USACE 2007a) contain Cemetery Creek, Ryan Creek, and an unnamed creek (Figure 5). Runoff associated with precipitation events flows to these established drainages and also over the face of the bluff, which can scour the highly erodible upper sandy layer. Cemetery Creek emerges from behind the Kenai Road beach area and discharges into the Kenai River near the western limit of the project area. Ryan Creek enters the Kenai River roughly 3,000 feet upstream from Cemetery Creek, near the center of the proposed project area (Tetra Tech 2007). A third, unnamed stream enters the Kenai River near the upstream limit of the bluff stabilization project. All three streams appear to drain the extensive wetlands to the north of the bluff and flow through the developed area between the river and the airport; Ryan Creek has been extensively channelized and even disappears underground for about 450 feet between Kenai Spur Road and Frontage Road. Cemetery Creek and the unnamed creek are catalogued as fish-bearing streams by the ADFG (see Section 3.9.2). Overland flow has been largely disrupted by development along the top of the bluff. Most of the local stormwater drainage from the top of the bluff is diverted into the City of Kenai s storm drain network. A small amount of surface drainage flows over the top of the bluff and down the bluff face, and several pipes protrude from the bluff face near the ground surface and discharge small amounts of water that run directly down the bluff face (Tetra Tech 2007). 17

37 Figure 5. Major Surface Drainages at Project Site The City of Kenai is located on the Nikishka Lowland geomorphological subdivision of the Kenai Lowland. This region is characterized by a modified morainal topography, which is separated by an interlacing pattern of swamps and muskegs developed in abandoned drainage channels and broad depressions. The topography and surface deposits of the region are primarily the products of repeated glaciations, which advanced from ice centers in the surrounding mountain ranges. Near the City of Kenai, the glacial moraines are fronted by a broad coastal plain consisting of terraced and channeled sand and gravel deposits, which terminate as steep sea bluffs above a series of raised tidal flats (USACE 2006a). Relatively thick unconsolidated glacial fluvial and marine sediments overlie bedrock in the project area. Bedrock occurs too deeply in the project area to impact design parameters for a selected alternative (USACE 2006 and 2007a). In addition, permafrost is absent, so it does not influence design. The area is within a regionally active seismic zone bisected by several active and inactive faults. The approximately 5,000 linear feet of receding Kenai Bluffs is readily identified by the general lack of vegetation on the bluff face, which exposes three distinct layers of sediment types. These exposed layers include: 18

38 2 feet of organic mat layer at the surface (top of the bluff) that is underlain by approximately 37 feet of medium dense sand with layers of sand with gravel alluvium, with a base consisting of 2 to 6 feet of gravel (lag deposit that transmits perched groundwater), and 36 to 45 feet of very hard lean clay containing sand and gravel (glacial till unit, with total thickness not reported). Groundwater discharge from the bluff is year round through the lag gravel at the base of the alluvium and through piping in the underlying till with a total potential flow rate of 7 to 10 million gallons per day. More localized flow is estimated to reach up to 400 gallons per minute in some areas (USACE 2006). The persistent groundwater seepage is readily visible about half way up the bluff at the interface of the alluvium and the glacial till deposits (Figure 6) and sporadic concentrated groundwater flow or piping daylights from the gravel lag deposits and the lower glacial till. Groundwater flow has been reported below the river s water level (USACE 2008a). Figure 6. Soil and Groundwater Conditions 19

39 The mouth of the Kenai River and adjacent seafloor of Cook Inlet is generally shallow and gently sloping with depths of less than 6 feet extending as far out as 2 miles from shore (Figure 7). Numerous rocks, shoals, and other navigation obstructions are present, including Salmo Rock and Kaluk Reef to the southwest. Figure 7. Depths near the Kenai River Mouth (Excerpt from NOAA Chart 16662) Semi-diurnal tides (two high waters and two low waters each day) influence the lower section of the Kenai River. Table 4 summarizes some tidal parameters for the Kenai River entrance. Below river mile 12, the Kenai River is subject to influence from semi-diurnal tides with two low waters and two high waters each lunar day. The tidal range at the Kenai Entrance in Cook Inlet is the fourth largest in the world at 31.4 feet (Table 4). 20

40 Table 4. Tidal Parameters Kenai River Entrance Parameter Elevation (ft MLLW) Highest Predicted Tide (16 October 1993) Mean Higher High Water (MHHW) Mean Tide Mean Lower Low Water (MLLW) 0.0 Lowest Predicted Tide (14 June 1995) -5.4 Wave attack on the bluff face is most pronounced near the river s mouth and decreases as the waves move inland. Wave modeling at the mouth of the Kenai River indicates that the wave height decreases from 4.5 feet to 2.5 feet along the affect bluff area as shown in Figure 8. Figure 8. Design Waves by Reach Both sea ice and river ice collect at the toe of the bluff during the winter months, although to what extent is dependent on temperatures, wind direction and intensity, tides, and ice concentration in Cook Inlet. The average river ice freeze-up is December 10 and the average ice break-up is April 2 (Mulherin, et al. 2001), and ice can close the river to vessel traffic for short periods from December to early April, according to NOAA s Alaska Coast Pilot 9. 21

41 The water quality of the Kenai River and its tributaries is monitored annually through the efforts of the ADEC, the Kenai Watershed Forum (KWF 2015), and several other agencies and organizations. In 2006, the ADEC listed the lower Kenai River as an Impaired Waterbody under Section 303(d) of the Clean Water Act; concentrations of fuel hydrocarbons detected in the river water had historically exceeded Alaska Water Quality Standards (AWQS; ref. ADEC 2016) for petroleum hydrocarbons, especially during the summer. The presumed source of the hydrocarbon contamination was the heavy traffic of motorized watercraft on the river during fishing season, particularly those with older two-stroke engines. The particular water quality standard that had been exceeded was Total Aromatic Hydrocarbons (TAH), the summed total concentrations of benzene, toluene, ethylbenzene, and xylenes. These compounds are major components of gasoline and contribute much to its toxicity, and TAH measurements provide a more sensitive and consistent means of evaluating gasoline contamination in water than attempting to quantify the concentration of total gasoline. The AWQS for TAH in the water column is 10 micrograms/liter (ADEC 2016). The ADEC began a program of annual water quality monitoring on the Kenai River in 2003 and has reported a marked decrease in TAH levels since then. Water samples collected in 2008 all complied with the TAH water quality criterion. The ADEC attributes the decrease in TAH levels to U.S. EPA hydrocarbon emissions standards for motorized watercraft that went into effect in 2006 and the gradual replacement of the older two-stroke motors with new 2006-compliant motors (ADEC 2010a). The ADEC removed the Kenai River from the Impaired Waterbodies list in 2009 after 2 years of demonstrated compliance with the AWQS. The Kenai River is famous for the turbid, milky appearance caused by its load of fine glacial silt, but construction and development along the river course suggest that human activities contribute to the sediment load (Figure 9). The marine waters of Cook Inlet entering the estuary at higher tides are also relatively turbid. Erosion from the Kenai Bluffs itself contributes an estimated 21,300 tons of sediment to the Kenai estuary annually. Sediments from the bank consist of a mixture of gravels, sands, silts and clays (USACE 2006a), with the finer materials adding to the turbidity within the estuary. 22

42 Figure 9. Kenai River estuary at the base of the eroding bluff showing highly turbid water. The AWQS for turbidity is 5 Nephelometric Turbidity Units (NTU) above background. However, the turbidity levels in the Kenai River are highly variable, and no background level has been established, so it is not possible to evaluate a given turbidity measurement against the water quality standard. The ADEC hydrocarbon monitoring program found ranges of 22 to 744 NTU in 2008, 7 to 19 NTU in 2007, and 14 to 735 NTU in 2003 across three stations along the river. The ADEC station at River Mile 1.5 (near the upstream end of the proposed bluff stabilization project) showed turbidity measurements that were generally less than 300 NTU, and which fluctuated less than at stations farther upstream (KWF 2015). The ADFG measured turbidity in the river channel adjacent to the proposed project site and found a pronounced gradient of lesser turbidity near the surface (between 50 and 100 NTU) and greater turbidity near the bottom (roughly 150 to 200 NTU) on two sampling events in April 2003 (ADFG 2004). Within the estuary, this gradient is probably explained by the lofting of sediment from the muddy channel bottom by tidal action. Within the Kenai River estuary, the level of salinity is dependent upon a complex interplay of tide phase, tidal amplitude, and river flow-rate. It is common in estuaries for out-flowing fresh water to overflow colder, denser seawater and form a distinct low-salinity layer at the surface. This type of stratification has been observed in the Kenai River estuary (ADFG 2004) but appears to be complicated by other factors such as seasonal temperature differences between the fresh and marine water, and the stratification may not always form or may exist only for brief periods. The ADFG study (ADFG 2004) found that during all months except April, salinities dropped from above 20 parts-per-thousand (ppt) to near zero ppt within 2 to 3 hours of high tide. In April, salinity remained above 10 ppt even at low tide. As with turbidity, the AWQS for 23

43 salinity is a set of allowable human-induced increases in salinity above natural conditions (ADEC 2016), but establishing a baseline natural salinity value for the estuary would be difficult. The AWQS for dissolved oxygen in fresh water is 7.0 mg/l or greater in waters used by anadromous or resident fish; in estuaries or tidal tributaries, the concentration may not fall below 5.0 mg/l unless there is a natural process that depresses dissolved oxygen content. The State has also established a maximum allowed dissolved oxygen concentration of 17 mg/l (ADEC 2016). The City of Kenai area enjoys generally good air quality due to a relatively low density of pollutant emission sources. There is no established ambient air quality monitoring program at Kenai for regulatory purposes, however, and little existing data to compare with the National Ambient Air Quality Standards (NAAQS) established under the Clean Air Act (CAA). These air quality standards include concentration limits on the criteria pollutants carbon monoxide, ozone, sulfur dioxide, nitrogen oxides, lead, and particulate matter. The city is not in a CAA non-attainment area, and the conformity determination requirements of the CAA would not apply to the proposed project at this time (ADEC 2015). Potential sources of air pollution include both non-point/mobile sources and fixed point sources. Major non-point source emissions would include particulates and carbon monoxide from cars, trucks, and boats, and also particulates from wood-burning stoves. The proposed project site has a commercial and residential area immediately to the north, and the Kenai River with its heavy summer boat traffic immediately to the south. Non-point source pollution can also come from natural phenomena, such as forest fires and volcanic eruptions. The State of Alaska has conducted air quality monitoring for particulates at one site in nearby Soldotna since 2011; this monitoring was prompted by observations of significant dust and smoke from wildfires in the summer (ADEC 2015). The town of Nikiski, about 9 miles north-northwest of the project site, has become a significant industrial center due to its proximity to the Cook Inlet oil and gas fields. A petroleum marine terminal, a petroleum refinery, a nitrogen fertilizer plant, and at least two electrical generation plants operate under CAA Title V permits as major potential pollutant sources. At least seven off-shore oil and gas platforms also operate under Title V permits. Several smaller oil and gas facilities exist several miles to the south of the project site in the Kalifornsky Beach Road area. The ADEC air quality division has occasionally received complaints or comments from area residents about emissions from these large industrial sources, but so far, has responded under the Title V program by policing individual emitters, as lack of funding has prevented implementation of an ambient air monitoring program for the Kenai region (Trost 2010, ADEC 2015). 24

44 Specific noise data does not exist for this area but is likely comparable with other similarly-sized coastal Alaskan communities. The project site is along a riverfront that is mostly light residential and commercial in nature. The Kenai Spur Highway is over 700 feet away from the project site at its nearest point to the bluff, and traffic on side streets leading to the bluff is generally light. Some noise is emitted from fish processing facilities on the eastern end of the bluff and from vessels transiting the river. Other noise is from wildlife, specifically birds. Human-generated noise increases during the personal-use fishery. 3.8 Bluff Erosion Rate Estimate and Mechanisms The USACE estimates the average erosion rate is 3 feet per year, with the estimated extent of erosion to the year 2057 shown in Figure 10 (Appendix B). Figure 10. Expected Erosion Extent in

45 The various erosion mechanisms acting on the Kenai Bluffs (Figure 11) include: Wind scour Groundwater seepage and piping Overland flow over the bluff Freeze thaw cycles Wave action and currents at the toe of the bluff The finer grained soils transported to the bluff toe from above are mobilized and transported away by riverine and tide currents during floodtides and storm surges (Figure 12). Since soil is not able to accumulate at the toe of the bluff, the lower portion of the bluff is exposed and susceptible to erosion during significant storm events at floodtides, which have the potential energy to damage the slope and remove larger material (Figure 12). As a result, the lower portion of the bluff erodes back and/or collapses, undercutting and collapsing the portion of the bluff above the flood tide elevation. These mechanisms keep the bluff slope steep and unstable. Vegetation does not establish and stabilize the bluff soil. Figure 11. Erosion Processes 26

46 3.9 Biological Resources Figure 12. Waves during a Storm Event at Kenai Bluffs The bluff face in the proposed project area is largely un-vegetated, as steady erosion has prevented plant communities from becoming established. Grasses, fireweed (Epilobium angustifolium) and other forbs, and a few woody shrubs such as alders (Alnus spp.) grow in isolated patches along the bluff face, often anchored in fragmentary mats of organic soil that have slid down the face. The bluff face vegetation is somewhat heavier in protected areas, such as the draw where Ryan Creek cuts through the riverbank, but is still discontinuous on the steeper portions of the bluff. As the bluff face erodes, the trees and their root balls become dislodged, leading to further destabilization of the bluff (Figure 13). 27

47 Figure 13. Trees and Root Balls Failing Vegetation on the existing ground surface along the top of the bluff is a patchwork of landscaped lawns and residential gardens, with pockets of original spruce (Picea spp.) and birch (Betula spp.) forest (Figure 14). The intertidal bench at the base of the bluff (Figure 15) consists of dense compacted sediment littered with boulders and debris, and is essentially devoid of established vegetation. During an April 2016 site visit, several small isolated patches of the marine alga Ulva intestinalis were found at the project site, but it is possible that this algae originated outside the estuary. Across the river from the bluff, the tidelands along the inside bend (named Chinulna Point on some maps) are sparsely vegetated, probably with low, salt-tolerant plants typical of the region such as arctic pearlwort (Sagina sanginoides), creeping alkali grass (Puccinellia phryganodes) and goose-tongue (Plantago maritime). Slightly higher, less-frequently inundated and icescoured areas of wetlands farther from the river channel are more heavily vegetated, most likely with communities that are dominated by sedges (Carex spp.), alkali grasses (Puccinella spp.), and arrow grasses (Triglochin spp.; Gracz, et al 2008, USFWS 1981). 28

48 Figure 14. Photograph dated 2001 showing typical distribution of vegetation along the face and top of the bluff. Figure 15. Photograph dated April 2016, showing intertidal zone at a low tide near 0.0 ft. MLLW The south bank of the river across from the bluff is categorized by USFWS as an Estuarine Intertidal Unconsolidated Shore (E2USN). Proceeding upriver the wetlands categorization transitions to include some Estuarine Intertidal Emergency Phragmites (Phragmites australis) 29

49 (E2EM5). The tidelands are sparsely vegetated, most likely with low, salt-tolerant plants typical of the region such as pearlwort (Sagina sanginoides), creeping alkali grass (Puccinellia phryganodes), and goose-tongue (Plantago maritime). Slightly higher, less-frequently inundated and ice-scoured areas of wetlands farther from the river channel are more heavily vegetated, most likely with communities that are dominated by sedges (Carex spp.), alkali grasses (Puccinella spp.), and arrow grasses (Triglochin spp.) (USFWS, 2010, Gracz, et al 2008, USFWS 1981). Invertebrates The USACE attempted to sample benthic invertebrates along the base of the bluff and in the Chinulna Point tide flats across the river in April Invertebrates were found in only one shallow sample of silt from Chinulna Point and consisted of a few small clams (Tellina nucloides). A later sample collected from the same area also contained a small number of Tellina nucloides as well as two marine polychaetes, probably Neris vexillosa. No benthic invertebrates were found in any of the seven sediment samples collected from the upper intertidal zone along the project footprint. The fine sediments on the intertidal portion of the estuary, especially along the outer bend of the river, proved to be very highly compacted and are not believed to support significant numbers of benthic organisms (USACE 2003a). Numerous attempts to obtain benthic invertebrate samples in the middle of the Kenai River channel failed despite using a variety of sampling devices deployed from a boat. The current, even at slack tide, made it nearly impossible for the dredge to land in an orientation where it could penetrate the highly compacted sediment on the river bottom. The USACE visited the project intertidal area in April No benthic sampling was attempted at that time, but the compacted fine sediments appeared to be unchanged from previous surveys. No visual signs of invertebrate use of the exposed sediments, such as worm or snail tracks, mollusk shells, or air holes, were found. As in the 2003 survey, numerous shorebirds were observed foraging in the mudflats on the south bank of the river directly across from the project area, but little or no such activity was seen on the north bank. The USACE s 2016 visit also specifically looked for signs of sessile epilithic organisms (e.g., barnacles, mussels, marine algae, etc.) inhabiting the boulders and cobbles scattered across the sediment of the project area. The rock surfaces were devoid of such organisms. An ADFG study in 2003 found significant numbers of invertebrates within the estuary waters, mostly shrimp (Crangon spp. and Neomysis spp.) and isopods (Saduria spp.). These invertebrates were especially prevalent in an April catch, when they were far more numerous than fishes, leading the investigators to surmise that invertebrates may dominate the estuary food-web through the winter months. These invertebrates become an important food source for fishes as the fish population increases through early summer (ADFG 2004). 30

50 Fish The ADFG maintains an online database of anadromous and fish-bearing streams, the Anadromous Waters Catalog (AWC; ADFG 2016c). As described previously, the Kenai River itself is a cataloged anadromous stream, as are many of its tributaries, including Cemetery Creek and the creek just downstream of Pacific Star Seafoods (Figure 5). The lower Kenai River is listed in the catalog as hosting the following species: Chum Salmon: present Coho Salmon: present Chinook Salmon: spawning Pink Salmon: spawning Sockeye Salmon: present Dolly Varden Trout: present Lamprey: present Eulachon: present Pacific Lamprey: present Whitefish: present The Kenai River is famous for its annual adult in-migrations (i.e., runs) of four species of Pacific salmon and is the most heavily used river in Alaska for recreational and personal-use fishing. The river supports two runs of Chinook salmon (Oncorhynhus tshawytscha) each year. The early run (averaging between 8,100 and 16,000 fish) usually enters the river in mid-may and ends by mid-june; the larger late Chinook run (averaging 56,000 fish) starts in early July. Between 7,000 and 30,000 Chinook salmon are harvested from the river each year. Sockeye salmon (O. nerka) also arrive in two runs, starting in late June and late July, respectively. The later sockeye run ends by early to mid-august and averages about 1 million fish. Coho salmon (O. kitsutch) arrive in several periods from late July through early October; about 41,000 cohos are caught each year. Pink salmon (O. gorbuscha) have a 2-year lifecycle and are much more numerous in evennumbered years. The pink salmon run lasts from late July through mid-august (ADFG undated factsheet, The Kenai River Pamphlet). Adult chum salmon (O. keta) are also sometimes found in the Kenai River but are not believed to spawn in the Kenai River system (ADFG 2016c). The Kenai River estuary is an important transitional habitat for salmon smolt as they adapt from fresh to marine waters during their out-migration in spring or early summer. Juveniles must develop the osmoregulatory capability to survive in salt water, while identifying new prey items and avoiding new predator species (ADFG 2004). Salmon do not spawn within the estuary, but several small streams entering the estuary have been identified as rearing habitat for juvenile salmon. Cemetery Creek (Figure 5) provides rearing habitat for silver, Chinook, and sockeye salmon, and the unnamed creek (catalogued by the ADFG as ) near the east end of the project area is identified as rearing habitat for coho and sockeye salmon (ADFG 2016c). 31

51 Other anadromous species found in the estuary include eulachon smelt (e.g., eulachon, Thaleichthys pacificus), longfin smelt (Spirinchus thaleichthys), and Dolly Varden (Salvelinus malma). The major eulachon in-migration occurs in May and June. Longfin smelt in the Kenai River (Figure 16) are at the extreme northern limit of their range; they are present in the estuary much of the year, but it is unclear whether they have a significant run in the Kenai. The smelt species are important food fish for adult salmon and other larger fish, sea mammals, and birds. Other marine and estuarine fishes common in the estuary include flounder, sole, sandlance, sculpin, and herring (ADFG 2004). Figure 16. Longfin Smelt Caught in Kenai River in 2002 (photo courtesy of Tim McKinley/ADFG). The 2004 baseline fisheries assessment (ADFG 2004) took samples in April, June, September, and December, and found finfish greatly outnumbered by invertebrates (shrimp and isopods, -) in April and in December. Longfin smelt were the most numerous fish present in the sparse April catch, while eulachon were dominant in June and September. In December, longfin smelt were the only fish caught. Juvenile salmon were captured in April, June, and September, but not in December (ADFG 2004). Birds The USACE conducted surveys for birds at the Kenai estuary on a near-monthly basis from April 2003 through March 2004; no surveys were conducted in December 2003 or in February 2004 (USACE 2003b). The majority of birds observed during these surveys were using the low headland and intertidal zone on the opposite side of the river from the bluff (Chinulna Point). This was presumably due to better feeding opportunities in the wetlands, broad mudflats, and sand bars present along the inside bend, and the less compacted sediments. The large sand and gravel bars that form opposite 32

52 the bluff are exposed to varying degrees with tidal movements, and corresponding fluctuations in the numbers of birds present were noted (USACE 2003b). The surveyors observed relatively fewer birds along the face of the bluff and the shoreline below. The most common birds along the bluff were common ravens (Corvus corax), black-billed magpies (Pica hudsonia), and small numbers of herring gulls (Larus argentatus). Swallows were sometimes seen flying along the bluff, but there was no indication that they nested in the riverbank at that location. Bald eagles (Haliaeetus leucocephalus) use spruce trees along the top of the bluff as vantage points to observe the river and the opposite shore (USACE 2003b). Gulls were the most abundant birds observed in the area at all times of the year, with over 1,000 present on some survey days. Most gulls were herring gulls, although a few mew gulls (Larus canus) and glaucous winged gulls (Larus glaucenscens) were also seen on occasion. Gulls are present along the inside bend across from the bluff throughout the year unless the river is frozen. Herring gull numbers peaked in July, and large numbers were seen nesting in the wetlands opposite the bluff. Nesting is possible in these wetlands during the summer months because the tides are not high enough during that time of year to inundate the area; these wetlands routinely flood during higher spring and autumn tides. USACE biologists noted during a May 14, 2003 visit that approximately 20 percent of gull nests contained an egg, while by August 21, most of the herring gull chicks had fledged. Therefore, peak use of the inside-bend wetlands by herring gulls appears to be from early May through the end of August. Gulls were also abundant along both banks at the mouth of the river in June and July, when they appeared to be attracted to discarded salmon carcasses (USACE 2003b). Bald eagles were most abundant in April and May (up to 70 were counted in a survey on May 1, 2003) but were practically absent during the summer. Eagles presumably disperse in the summer to nest and take advantage of abundant salmon runs in shallower streams elsewhere throughout Southcentral Alaska (USACE 2003b). Common goldeneye (Bucephala clangula) were the most numerous waterfowl species in late winter, with up to 77 seen during one day s survey in March The goldeneye tended to congregate in open water upstream of the bluff unless forced downstream by ice. Mallards (Anas platyrhynchos) were also occasionally seen in large groups in the late summer and autumn. Large flocks of migrating Canada geese (Branta canadensis) and other waterfowl use the grassy inner-bend wetlands, especially as this area is free of ice and snow earlier in the spring. Waterfowl species seen in smaller numbers included northern pintail (Anas acuta), green-wing teal (Anas crecca), and snow goose (Chen caerulescencs). Wading birds observed included yellowlegs (Tringa spp.), dunlin (Calidris alpine), dowitchers (Limnodromus spp.), and rock sandpipers (Calidris ptilocnemis; USACE 2003b). 33

53 Mammals The developed uplands surrounding the Kenai River estuary may be described as a mix of residential, commercial, and light industrial, and offer limited habitat for large terrestrial mammals. Likewise, the sparsely vegetated intertidal areas around the estuary provide little food or cover, but more suitable habitat is found in the marshlands farther upstream. A coyote (Canis latrans) was spotted between the Warren Ames Bridge and the public boat launch during a USACE survey in May 2003 (USACE 2003b), and rodents such as muskrat (Ondatra zibethicus) probably make use of the grassy wetlands in the more heavily vegetated stretches of the estuary. Caribou (Rangifer tarandus) and moose (Alces alces) are also commonly seen in the marshlands well upstream of the project site. Harbor seals (Phoca vitulina) are routinely seen near the mouth of the Kenai River in small numbers, although large gatherings have been reported farther upstream. The USACE survey observed seals in the river in all survey sectors, and they may range several miles upstream. At low tide, seals were typically hauled out on large boulders in Cook Inlet outside the mouth of the river (USACE 2003b). Beluga whales (Delphinapterus leucas) are occasionally spotted within the estuary. They are most likely to enter the estuary on an incoming high tide and are easily visible from popular public viewing points on the beach north of the river mouth, at the Kenai City Dock, and near the Warren Ames Memorial Bridge, roughly 5 river-miles upstream from the river mouth (ADFG 2016b). Cook Inlet beluga whales are discussed further in section Protected Species The only species listed as endangered or threatened under the Endangered Species Act (ESA) likely to be encountered near the project site is the beluga whale, Delphinapterus leucas (NMFS 2016a, USFWS 2016a). The Cook Inlet Distinct Population Segment (DPS) of beluga whales was listed as endangered under the ESA in October 2008 after rapidly declining numbers failed to respond to restrictions on subsistence hunting begun in The population continues to show a negative trend, with a 2014 survey estimating 340 individuals, down from an estimated 1,293 whales in 1979 (NMFS 2015). The designation of critical habitat for Cook Inlet belugas was finalized in April 2011 (50 CFR part ). Their critical habitat is divided into two areas, with Area 1 representing the northern extremity of Cook Inlet where the whales concentrate during the summer months, and Area 2 encompassing the wider distribution of Cook Inlet belugas through Cook Inlet in the winter and early spring (Figure 17). The Kenai area falls into Area 2, with the Kenai River estuary up to the Warren Ames Bridge (roughly 5 river-miles upstream from the mouth of the Kenai River) specifically designated in the ruling as critical habitat. In addition, the NMFS identified the following primary constituent elements (PCEs) essential to the conservation of the Cook Inlet beluga whale (NMFS 2015): 34

54 1. Intertidal and subtidal waters of Cook Inlet with depths less than 30 feet mean lower low water (MLLW) and within 5 miles of high and medium flow anadromous fish streams. 2. Primary prey species consisting of four species of Pacific salmon (Chinook, sockeye, chum, and coho), Pacific eulachon, Pacific cod, walleye pollock, saffron cod, and yellowfin sole. 3. Waters free of toxins or other agents of a type and amount harmful to Cook Inlet beluga whales. 4. Unrestricted passage within or between the critical habitat areas. 5. Waters with in-water noise below levels resulting in the abandonment of critical habitat areas by Cook Inlet beluga whales. The proposed project is within critical habitat for Cook Inlet beluga whales since it is located downstream of the Warren Ames Bridge. The proposed with project footprint for the rubblemound structure alternatives is an intertidal bench (berm) along the base of the bluff, above MLLW but at least partially below mean high water (MHW), the upland boundary for marine critical habitat areas. 35

55 Figure 17. Cook Inlet Beluga Whale Habitat Areas (Source: NOAA) Cook Inlet belugas show distinct seasonal shifts in distribution and habitat use, generally congregating in the northernmost portions of Cook Inlet during roughly June through October, then dispersing through a wider area of Cook Inlet the rest of the year (NMFS 2015). Opportunistic sightings reported to and cataloged by the NMFS suggest that the lower Kenai River is most heavily used by Cook Inlet belugas during the months of March through May; of 64 such sightings reported between 2007 and 2015, 36 occurred in April alone, primarily in the latter half of the month (Shelden 2016). This spike in beluga activity within the Kenai River roughly corresponds with the river s April-June run of Pacific eulachon, a vital early-year food 36

56 resource for Cook Inlet belugas. The presence of other prey species such as longfin smelt in the early spring estuary (ADFG 2004) may account for the March and early April Cook Inlet beluga use of the Kenai River ahead of the main eulachon run. No sightings were reported to NMFS in July or August from 2007 to 2015, despite the heavy in-migrations of adult salmon that occur during these months. This is consistent with the known summer concentration of Cook Inlet belugas at the north end of Cook Inlet, away from the Kenai area, and with speculation that the intense human fishing activity on the lower Kenai River during these salmon runs may deter belugas from the river at that time (Sheldon 2016, NMFS 2015). According to some descriptions, the project area is within the range of the endangered short tailed albatross (Phoebastria albatrus; USFWS 2016). While this species ranges across much of the North Pacific Ocean, it is associated with the open ocean, concentrating along the break of the continental shelf where upwelling and high primary productivity result in abundant preferred prey such as squid and pelagic fishes. The confined inland waters of Cook Inlet and the Kenai River estuary do not provide usable habitat for this species (USFWS 2008), and it would not be expected to appear within Cook Inlet except as a rare, vagrant individual. The following species protected under the Marine Mammals Protection Act (MMPA), but not listed under the ESA, are known to be present in the Kenai River estuary at least occasionally: Harbor seal (Phoca vitulina) Harbor porpoise (Phocoena phocoena) Killer whale (Orcinus orca) Harbor seals are a common sight within the Kenai River estuary and have been spotted many miles up-river. They may be present in the estuary at any time of year. Seasonal patterns of harbor seal use of the Kenai River estuary are not well understood. Data on their numbers are collected opportunistically, and the seals low profile and quick movements within the turbid river waters make them difficult survey subjects. Harbor seals are most conspicuous when hauled out onto shore, which they occasionally do in masses of hundreds of individuals within the estuary. As many as 340 seals were counted in a November 2013 group hauled out across from the Inlet Seafood processing plant, and another sighting of over 200 was made in the same area in November Another major haulout location is just upstream of a wildlife viewing platform near the Kenai City Dock. Both of these identified haulouts are a mile or more upstream from the project site. A few individual seals can often be seen hauled out on the mudflats directly across the river from the proposed project site and on sandbars and rocks just outside the river s mouth, but no reports exist of the project area itself being used as a haulout (Figure 18; London 2016). The rocks and debris strewn on the project site below the bluff, and the flatter-grade shorelines existing nearby, conceivably make the project site less attractive for hauling-out than other readily available options. 37

57 Figure 18. Harbor Seal Haul-out Areas Reported in the Kenai River Estuary (in blue). Killer whales are known from a handful of reports to occasionally enter the Kenai River estuary, presumably in pursuit of salmon or marine mammal prey. Harbor porpoises are spotted within the Kenai River, but little is known about their use of the river. Bald eagles present at the Kenai River estuary are protected under the Bald and Golden Eagle Protection Act as well as the Migratory Bird Treaty Act (see below). In addition to prohibiting direct takes such as killing eagles or destroying nests, this act also regulates human activity or construction that may interfere with eagle s normal breeding, feeding, or sheltering habits (USFWS 2007). There are no currently known bald eagle nesting sites in the project area; the closest nesting site recorded by the USFWS is about 0.8 mile to the southeast (Lewis 2016). A limited number of trees large enough to be suitable for eagle nesting are available along the top of the bluff, mostly at the Ryan Creek drainage. 38

58 With the exception of State-managed ptarmigan and grouse species, all native birds in Alaska (including active nests, eggs, and nestlings) are protected under the Federal Migratory Bird Treaty Act (MBTA; USFWS 2009) Special Aquatic Sites and Waters of the United States The U.S. EPA identifies six categories of special aquatic sites in their Clean Water Act (CWA) Section 404 (b)(1) guidelines: Sanctuaries and refuges; wetlands; mud flats; vegetated shallows; coral reefs; and riffle and pool complexes. Special aquatic sites do not exist within the project footprint. The foot of the eroding bluff face, while regularly inundated, does not meet the USACE jurisdictional definition of a wetland as it is devoid of established vegetation (ERDC 2007; WES 1987). What vegetation is present is generally displaced fragments of upland growth that are regularly swept away, rather than supported, during the floodtides. Cemetery Creek, to the west of the project site, supports obvious estuarine wetlands. The surface sediments at the project site are predominantly sand, gravel, and rocky debris eroded from the bluff face, rather than fines deposited by the river, and appear to host very little biological activity. The project site does not meet the definition of a mud flat under Section 404 (b)(1) guidelines, although extensive mud flats do exist along Chinulna Point across the river from the project site. The U.S. Fish and Wildlife Services National Wetlands Inventory (NWI; USFWS 2016b) regards the eroding bluff face on the north side of the river as uplands. The NWI identifies broad areas to the south and west of the proposed project area as different types of estuarine, marine shoreline, or in-water habitat based upon the type of vegetation present, the substrate, and frequency of inundation (Figure 19). The alphanumeric codes on the map refer to specific habitat parameters that will not be elaborated upon here. The footprint of the berm or revetment alternatives generally avoids areas that are designated as wetlands in the NWI, although construction access to the project site from the west would need to be designed to avoid impacts to small areas of estuarine wetlands near the mouth of Cemetery Creek (Figure 19). Any portion of the project constructed below mean high water would be within waters of the United States, and would be subject to Section 10 of the River and Harbors Act of Placement of material below the high tide line would be subject to Section 404 of the Clean Water Act. 39

59 Figure 19. An Annotated National Wetlands Inventory Habitat Map of The Kenai River Estuary, Generated at the NWI Website (USFWS 2016) Essential Fish Habitat The NMFS designated the marine waters of Cook Inlet as Essential Fish Habitat (EFH) for salmon; this designation extends to all estuarine and freshwater bodies necessary for the development of salmon, including the Kenai River (NMFS 2016b, NPFMC 2012). The Kenai River is a catalogued anadromous stream, as are many of its tributaries. The lower Kenai River is listed in ADFG s anadromous stream catalog as hosting the following species: Chinook salmon (Oncorhynchus tshawytscha), chum salmon (Oncorhynchus keta), coho salmon (Oncorhynchus kisutch), pink salmon (Oncorhynchus gorbuscha), sockeye salmon (Oncorhynchus nerka), Dolly Varden (Salvelinus malma), lamprey, eulachon (Thaleichthys pacificus), Pacific lamprey (Entosphenus tridentatus), and Alaska whitefish (Coregonus nelsonii). While listed in the AWC as spawning in the lower Kenai River, Chinook salmon and pink salmon are not understood to spawn in the Kenai River estuary itself. The catalog lists Cemetery Creek as providing rearing habitat for coho, Chinook, and sockeye salmon, and the unnamed creek shown in Figure 5 (catalogued by the ADFG as ) near the east end of the project area as rearing habitat for coho and sockeye salmon. The Ryan Creek drainage is not cataloged as an anadromous stream (ADFG 2016c), although some observations suggest that juvenile fish may use its intertidal channel as rearing or refuge habitat (Sinclair 2016) Cultural and Historic Resources The Kenai Peninsula has been inhabited by indigenous peoples for at least 7,500 years (Reger 2003). A Dena ina Kenaitze community was already well-established at Kenai when the first 40

60 Russian fur traders arrived in Russians established the Nikolaevskii Redoubt near Kenai in 1786 (Znamenski 2003). This long occupation has resulted in both historic and prehistoric sites existing along the top of the river bluff. There are five historic properties within the project area identified on the Alaska Heritage Resources Survey, maintained by the State Historic Preservation Office: three historic houses and two archaeological sites. One of these archaeological sites is known to contain a late nineteenth-century cemetery, which is at risk of eroding into the river. At least one of the two known archaeological sites along the river bluff includes both prehistoric and historic components. This archaeological site, located on Federal Aviation Administration (FAA) and City of Kenai land east of the Senior Center, is called Shk ituk t (Alaska Heritage Resources Survey [AHRS] number KEN-020). Identified on Petroff s 1884 map as Chkituk, it was the primary Dena ina settlement in the area until it was abandoned shortly after the Holy Assumption of the Virgin Mary Russian Orthodox Church was built in During World War II, the Civil Aeronautics Administration bulldozed much of the site, including the village s Old Russian Orthodox cemetery, in order to build an airstrip (Boraas 2009). Despite the surface modification of the site, some house depressions remained into the 1950s, and there is a high probability that intact subsurface deposits remain (USACE 2007b; Boraas 2009). The site is considered a traditional cultural property by members of the Kenaitze Indian Tribe (Pierce 2016; USACE 2011, 2007, 2004b). The second archeological site is located in a forested area on the western edge of Ryan Creek draw. It contains at least three house depressions and multiple cache pits, and is thought to be the remains of a former village site called Kili Betnu (AHRS number KEN-710). Additional prehistoric house depressions have been identified eroding off the bluff edge (USACE 2011, 2007, 2004b). A survey of historic buildings was conducted in 1996 for the City of Kenai, but it was confined to the Kenai Townsite Historic District, and stopped short of most of the area near the eroding bluff (Elliott and Lane 1996). However, three historic buildings identified during the survey area do occur within the 50-year erosion line: Hermansen-Miller House, built in 1916 (AHRS number KEN-279) Kenai Log Cabin #2, built in 1924 (AHRS number KEN-070) Showalter House, built in 1936 (AHRS number KEN-276) At least 13 other buildings within the 50-year erosion zone along the top of the bluff appear to be historic, but have not been evaluated. Some of these were built using the Swedish cope logging technique, and are believed to have been built and lived in by Nordic cannery workers (in fact, this area was called Swede Town ). Other buildings have modern siding that conceals the log construction, but are known by locals to be traditional log structures (USACE 2007). The importance of many of these buildings is clear. For example: 41

61 The Mann/Peters House was originally built in 1952 by Harry James Mann, a local Alaska Native leader, commercial fisherman, and member of the Laborers Union (USACE 2011). The Kenai Bible Church, the first Protestant church in Kenai, was built in Today it remains an active church, and has a lighted cross that is seen as a guide to many fisherman entering the river (USACE 2011). Kenai Joe s Bar (formerly Keen-Eye Joe s ), established in 1940, was popular in the 1940s and 1950s, and is known locally as an drinking establishment (USACE 2011, 2007). In addition to the standing historic buildings, four unknown historic structures were identified in 2003, perched at the edge of the bluff. They have since disappeared down the eroding bluff face (USACE 2011, 2004b) Subsistence Activities The Kenai River and its salmon fishery is designated a non-subsistence area by the Alaska Board of Fisheries and Game. After a 1992 court case decision made all Alaskans eligible subsistence users, the Board moved to protect some particularly valuable fisheries from exclusive subsistence use by declaring them to be non-subsistence areas, then establishing individually-regulated personal use fisheries. The Kenai River has one of five personal use fisheries in upper Cook Inlet. The Kenai dip net fishery is currently open from July 10 through July 31, from 6 a.m. to 11 p.m. Alaskans harvest between 130,000 and 540,000 sockeye salmon annually in this fishery. The number of salmon escaping upstream to spawn is closely monitored, and the personal use fishery may be restricted if ADFG projects that salmon escapement goals may not be met (ADFG 2016a). Figure 20 shows the project site location relative to areas open and closed to personal use dip netting. 42

62 Figure 20. Kenai River Personal Use Fishery Regulation Areas (adapted from ADFG 2016a). The Kenaitze Indian Tribe operates an educational fishery in the lower Kenai River, permitted by the State of Alaska in lieu of a rural subsistence fishery. The purpose is to teach and preserve the cultural traditions of subsistence within the Kenaitze community. The Educational Fishery is allowed a total annual quota of 8,000 fish, including 300 Chinook salmon and 500 coho salmon. The program is permitted to place set-nets at two locations near the mouth of the river; individual tribe members may request to be assigned a tide in which they fish these locations. The Kenaitze Indian Tribe operates this fishery from May through November, and the catch is shared within the Kenaitze community and with allied groups (Kenaitze Indian Tribe 2016). 4.0 FUTURE WITHOUT-PROJECT CONDITIONS The future without-project conditions mirror those under the No Action Alternative. Absent Federal action it is unlikely that another entity will take action due to budgetary constraints. The expected without-project conditions form the basis of evaluation against with-project conditions and are presented below. 43

63 4.1 Economic Conditions Absent Federal action, damages to land, structures and infrastructure, as well as loss of recreational value are expected to continue. The following sections describe the damage categories and estimate their value over the 50-year period of analysis. Applying an appropriate discount rate and period of analysis make damage values comparable on the equivalent time value of money. All values are reported as present values based on the Federal Fiscal Year 2017 discount rate of percent and a 50-year period of analysis. Additional details of future without project economic conditions are in Appendix C. Approximately 5,000 feet of riverbank bluff is eroding at an average annual rate of 3 feet per year. It s assumed that once the erosion reaches 50 percent of the total lot size, no buyer would be willing to take the risk of purchasing the lot. There are 59 lots expected to reach this level of loss over the 50-year period of analysis. At current erosion rates, the Kenai Bluffs will continue to lose 0.34 acres of land per year, and 17.2 acres over the 50-year period of analysis. Valuation of lost land is based on an analysis of the average value per acre of comparable parcels within the KPB against the average value per acre of parcels within the erosion zone. Using this approach, expected future without-project land damages over the period of analysis have a present value of $1.0 million and equivalent average annual damages of $39,000. Table 5 summarizes expected land damages from erosion in ten year increments. Table 5. Future Without-Project Land Damages Years Item Total Area (acres) Present Value $331,000 $249,000 $188,000 $141,000 $107,000 $1,016,000 Average Annual Damages $39,000 As a result of continued bluff erosion at the expected erosion rate, it is estimated that 31 properties containing structures and/or non-structural improvements in proximity to the bluff would be condemned over the period of analysis. These properties include a total of 34 structures and 23 other non-structural improvements. Some properties within the erosion zone have not been fully developed but are not considered vacant land. These properties have improvements including gravel driveways that have been installed, greenhouses, or land development such as fill being placed, etc. Damages to improved properties have been incorporated into the structural damages benefit category. 44

64 Future without-project damages to residential, commercial, and public structures over the 50- year period of analysis have a present value of $9.5 million and average annual damages of $362,000. The largest structure within the project area is the Kenai Senior Citizen Center, which has a 2016 assessed value (land plus improvements) of approximately $7.9 million. At current erosion rates, the Senior Center is expected to suffer catastrophic damage within the next 20 years. Table 6 summarizes future-without project structure damages. Table 6. Future Without-Project Structure and Non-Structural Improvement Damages Type Present Value Average Annual Residential $2,651,000 $101,000 Commercial $1,634,000 $62,000 Public $5,235,000 $199,000 Total $9,520,000 $362,000 Infrastructure damages due to erosion are also expected to occur during the period of analysis. Threatened infrastructure includes roads, signs, street lights, curbs/gutters, water mains, sewer lines, lift stations, man holes, culverts, storm drains, and various utility lines (gas, electric and telecom). Please see the Economics Appendix for details on infrastructure damages. Relocation of utilities and roads is expected to continue in the absence of a project. It is estimated that at least an additional 1,000 feet of road and utility lines are at risk of erosion. These roads and lines are anywhere from 30 to 100 feet from the bank. At the current pace of erosion, additional streets, sewer lines, and other infrastructure noted above would need to be replaced within approximately 10 to 20 years. As a result of continued bluff erosion at the expected average annual rate of 3 feet per year, estimated infrastructure damages from erosion over the period of the analysis have a present value of $1.8 million and average annual damages of $67,000. This section describes the value of recreational activities along Kenai Bluffs as they are expected to exist in the absence of a Federal project. This value serves as a baseline for which to evaluate the beneficial increase in future recreation opportunities that would occur under the various future with-project scenarios. The bluff offers unparalleled views of the Kenai River and Cook Inlet, and is often traversed by local residents and tourists for wildlife viewing and other outdoor activities such as hiking, biking, dog walking, or cross-country skiing along the roads and natural paths. Absent Federal action, these activities would be replaced by lower value activities pushed back to roads and properties farther inland from the bluffs. The amazing views afforded by the bluffs would be 45

65 impeded, not fully, but to a large extent by remaining structures. Additionally, views may be further depreciated by condemned (but not demolished and picked up structures) as erosion causes properties to be lost. The value of recreation opportunities is measured by Unit Day Value calculations, which are described in detailed in the Economics Appendix and Recreation Addendum. Unit Day Value points are calculated based on criteria that address the quality of the recreational area, the number and types of activities enjoyed in an area, and the availability of substitutes nearby. The UDV method then uses this point system to determine day values for recreation. Using this approach, the recreation experience at Kenai Bluffs has a present value of approximately $10.3 million and average annual value of $390,000 over the 50-year period of analysis. 4.2 Environmental Conditions Absent Federal action, the bluff is expected to continue to erode at an average rate of 3 feet per year. The sediment from the resulting erosion will be deposited into the river, feeding the estuary and tidal lowlands. 4.3 Climate Change Short observational records in Alaska make it difficult to separate climate change from natural multi-decadal variability. There are also quality problems, especially for measurements of precipitation and discharge. While there is evidence of a statewide average temperature increase of approximately 3 degrees Fahrenheit over the last 60 years, there are few spatially coherent trends in precipitation (McAfee et al. 2013). Thus, an increase in precipitation and resulting changes in stream discharge for this study area are considered unlikely. 4.4 Cultural Resources In the absence of a project to address erosion, the only way to protect important cultural resources would involve full salvage recovery operations and Historic American Building Survey (HABS) recordation. There are five known historic properties identified on the Alaska Heritage Resources Survey within the project area that are expected to be impacted in the futurewithout project scenario. These properties includes three historic houses and two archaeological sites, one of which is known to contain a nineteenth-century cemetery. In addition to the five known historic properties, there are 13 additional historic buildings of unknown significance within the 50-year erosion zone. These buildings have not been evaluated for eligibility for listing on the National Register of Historic Places; evaluation would require surveys and archival research. The activities described above regarding the mitigation of adversely affected cultural resources are not expected to take place in the future-without project scenario. The USACE archaeologist indicated that there are no known plans for salvage archaeological operations or documentation of historic buildings along Kenai Bluffs, whether undertaken by the City of Kenai or other 46

66 entities. Therefore, costs associated with these activities are not considered as future-without project losses. These costs would be incurred in future-with project scenarios for alternatives that would impact these resources. These impacts are discussed in detail in the Economics Appendix. 4.5 Political Conditions The State of Alaska Department of Labor and Workforce Development projects the KPB as a whole to gain approximately 9,000 residents over the next 30 years (Table 7). The degree to which this increase occurs, specifically in the greater Kenai area, is dependent upon a number of factors. The city s relative proximity to Anchorage, access to marine recreation, and rural lifestyle while maintaining common services and conveniences makes it an attractive location for some future development. However, a significantly large increase in development and population is not expected. Table 7. State of Alaska Population Projections for the Kenai Peninsula Borough Year Population Increase ,756 N/A ,225 2, ,391 2, ,116 1, ,321 1, , , Because of this relatively stable environment, the prevailing economic and political conditions are not expected to change significantly over the period of analysis. 4.6 Summary Without-Project Conditions Absent Federal action to prevent erosion, the above-detailed damages will continue to accrue. The present value of the expected damages to structures, land, and public infrastructure, as well as lost recreation value due to erosion is approximately $22.6 million with an average annual value of $858,000. Table 8 summarizes the future without-project condition at Kenai Bluffs and forms the basis for comparison for the future with-project alternatives. Table 8. Summary of Future Without-Project Conditions Category: Present Value Average Annual Structures $9,520,000 $362,000 Land $1,016,000 $39,000 Public Infrastructure $1,768,000 $67,000 Damages Subtotal $12,304,000 $468,000 Recreation Value $10,285,000 $390,000 Total $22,589,000 $858,000 47

67 5.0 FORMULATION AND EVALUATION OF ALTERNATIVE PLANS 5.1 Plan Formulation Rationale Plan formulation is the process of building alternative plans that meet planning objectives and avoid planning constraints. Alternatives are a set of one or more management measures functioning together to address one or more planning objectives. A management measure is a feature or activity that can be implemented at a specific geographic location to address one or more planning objectives. A feature is a structural element that requires construction or assembly on-site whereas an activity is defined as a nonstructural action. 5.2 Management Measures During the planning charrette held May 4-5, 2015, a number of measures were identified. The relative merits and drawbacks of each measure were examined with measures screened out as appropriate based on agreed upon criteria and associated metrics. Measures were screened using the four national criteria and three study specific criteria, discussed in section 2.5. In addition each proposed measure was evaluated against the general metric whether the design would address/control the major mechanisms causing the erosion and receding bluff (groundwater seepage, overland flow, freeze thaw cycles, and wave action and currents at flood tides) as identified in section Of these erosion mechanisms, wave action and currents at flood tides have been identified as key to eventual bluff stabilization. Specific engineering design criteria used to develop the measures are presented in detail Appendix B. Structural measures are generally those measures that reduce the probability of erosion. Sixteen measures initially considered for this project are presented in Table 9, with those that were removed from future consideration (i.e., screened out) are shown in red with strikethrough. Table 9. Structural Measures Considered Groundwater Pumping Longitudinal Dike Toe Protection (Armoring) Breakwater Gabions Toe Wall (Sheet Pile, etc.) Shotcrete Beach Channel Training Nourishment Measures Relocate River Dredging Upper Slope Mouth Stabilization Groundwater Conveyance Regrading/Revegetation Groundwater Cutoff Wall Top-of-Bluff Drainage 48

68 The reason or reasons measures from Table 9 were screened out vary, but most were removed due to ineffectiveness, cost, or feasibility. The main reason or reasons why these measures were screened out are presented below: Groundwater pumping alone influences one erosion mechanism and would be ineffective since it does not prevent the material that accumulates at the toe of bluff from washing away during floodtides. This measure would also be a long-term continuous maintenance cost to maintain pumping well. A breakwater would be ineffective at preventing flood tides from reaching the toe of the bluff and washing away material accumulating at the toe of the bluff. It is also thought to be cost prohibitive because of the size of the structure needed to combat coastal storms, and it could be a potential navigational and commercial fishing hazard. Shotcrete is a process where a cement or cement like mixture is sprayed on the surface to support and protect the surface. The effectiveness or chance of success of this measure would likely be limited due to the groundwater, the severe coastal environment, and freeze thaw cycles attacking the shotcrete surface. Gabions are rock filled wire enclosures that have the potential of using smaller less expensive rock for barriers; however, the wire would be subject to salt water corrosion and are not proven in marine environments. Beach nourishment relies on a source of material, typically a soil type matching the existing beach material; however, this method would not be effective because the main erosion mechanism during flood tides would likely cause an unacceptably high frequency of replenishment. In addition, a dependable cost-effective material source could not be readily identified for this measure to be effective. Toe wall or sheet piling has the potential for stabilizing the toe of the bluff; however, there was a concern that a vertical wall would cause rebound waves that could become a navigation hazard to small boat traffic. Channel training, in general, includes dredging or installing a structure that controls the channel. This measure would be ineffective because the river channel is not the main erosional mechanism that destabilizes the bluff. A groundwater cut-off wall as single measure would be ineffective because it does not address the main erosion mechanism. In addition, as groundwater eventually migrates around the wall, resulting in additional seepage in local drainages, there is the potential of unintended consequences, such as destabilizing the slope and enhancing erosion rates in these areas. Non-structural measures are those measures that reduce the consequences of erosion through relocations, buyouts, and demolition with reconstruction (within authority granted by Section 49

69 116). Five measures initially considered for this project are presented in Table 10 with those that were screened out shown in red with strikethrough. Table 10. Non-Structural Measures Extended No-Wake Zone Demolish/Rebuild Structures Relocations Zoning Changes Buyouts The extended wake zone was screened out because it would be ineffective since it does not address flood tides as the main erosion mechanism that prevents the bluff from stabilizing 6.0 Alternative Descriptions The following measures were carried forward on their merits to address the major erosion mechanisms at the project area, including wave action, flood tide currents, groundwater seepage, overland flow, and freeze thaw cycles: Longitudinal dike, toe protection, groundwater conveyance, re-vegetation, dredging, upper slope stabilization, top-of-bluff drainage, and river mouth relocation. Based on the measures that were carried forward, the six combinations of measures, or alternative plans are listed below: Alternative 1: No Action Alternative 2: River Mouth Relocation Alternative 3: Revetting and Vegetating the Bluff Face - Buried Toe Alternative 4: Revetting and Vegetating the Bluff Face - Weighted Toe Alternative 5: Protective Berm at the Bluff Toe Alternative 6: Structure Relocation Each alternative plan is described in more detail in the following sections. 6.1 Alternative 1: No Action This alternative takes no action to reduce or halt bluff erosion at Kenai. The study objectives are not met and no opportunities are realized. The bluff continues to erode. Structures continue to be lost as the ground beneath them erodes away. These structures include historical structures, the Senior Center and Senior Housing, commercial buildings, and residences. Cultural resources associated with the Dena ina people in general and the Kenaitze Tribe in particular are lost. Public utilities and properties suffer damages as described in the Future-Without Project conditions. As above, specialized recreation opportunities for viewing wildlife and traversing the bluff area are also lost or lose value. 6.2 Alternative 2: River Mouth Relocation River Mouth Relocation is a construction alternative that relocates the mouth of the Kenai River approximately 3,500 feet to the south (Figure 21). A new channel is dredged and the material stockpiled during excavation. Once the excavation is complete, the existing channel is filled in along the active erosion area to create emergent wetlands. Jetties are constructed to redirect river 50

70 flow. Erosion of the bluff is reduced due to the reduction of waves, river currents, and tidal action from the bluff area. However, erosion would continue to occur to some degree due to groundwater seepage and overland flow. Some buyouts, relocations, and/or structure replacements are required within the new threatened area, though they are less than the number required under the Non-Structural Alternative. A harbor and associated channel could be created north of the new river mouth (Figure 22), capturing navigation opportunities. However, since this study does not have the authority to construct navigation features that are eligible for cost-sharing, the harbor and associated channel would remain non-federal. Navigation benefits claimed from creation of this harbor would be incidental to construction of coastal storm risk management measures. Maintenance dredging is required with this alternative on an annual basis. It is also assumed that a portion of armor stone will need to be replaced to maintain the jetties. Significant loss of stone from the structure over the period of analysis is not expected, and is estimated at approximately 28,160 cubic yards of armor stone every 20 years. The total economic (NED) cost including interest during construction and maintenance has a present value of approximately $592 million or $22.5 million annually over the period of analysis. 51

71 Figure 21. Plan View of River Mouth Relocation 52

72 Figure 22. Channel Requiring Maintenance Dredging 6.3 Alternative 3: Revetting and Vegetating the Bluff Face- Buried Toe Alternative 3 addresses the erosion mechanisms by constructing over approximately 5,000 feet of bluff face (Figure 23) by: Cutting and filling the bluff to a more stable slope Constructing a stone revetment at the base of the bluff with a buried toe Vegetating the bluff slope above the revetment The typical section for Alternative 3 (Figure 24), shows the armoring would extend from a buried toe 6 feet below the current river bank to a height of feet MLLW. Filter fabric material and geotextile would be used to ensure proper filtering of groundwater seepage. The 53

73 revetment height would gradually decrease in height from zone A to zone C (Figure 8) to account for the decrease in wave height further upstream. Alternative 3 requires the buyout or relocation of approximately 25 structures at the top of the bluff in order to facilitate a cut back to a stable slope of 2H:1V, starting from approximately +65 feet MLLW from the bottom of the revetment. A temporary easement at the top of the bluff would be needed for construction of the revetment. It is not anticipated that there would be a significant loss of stone from the structure over the period of analysis. It is estimated that approximately 1,350 cubic yards of armor stone would need to be replaced every 20 years. The total economic (NED) cost, including interest during construction and maintenance, has a present value of approximately $54.5 million or $2.1 million annually over the 50-year period of analysis. Figure 23. Alternative 3 Plan View - Revetment with Buried Toe 54

74 Figure 24. Alternative 3 Typical Section Revetment with Buried Toe 6.4 Alternative 4: Revetting and Vegetating the Bluff Face- Weighted Toe The design for Alternative 4 is similar to Alternative 3 in that it addresses the erosion mechanisms by constructing across the approximately 5,000 feet of bluff face (Figure 23) by: Cutting and filling the bluff to a more stable slope Constructing a stone revetment at the base of the bluff as a weighted toe rather than a buried toe Vegetating the bluff slope above the revetment However, the typical section for Alternative 4 (Figure 25) indicates that this alternative reduces the volume of material cut from the bluff and uses fill at the base to create a stable slope. The stone revetment at the base of the fill area is not buried. Filter fabric separates the filter rock from the native material. The revetment height gradually decreases in height from zone A to zone C (Figure 8) to account for the decrease in wave height farther upstream. The toe of the revetment is designed to launch material placed on the river side of the revetment to fill potential scour holes. This alternative requires the buyout or relocation of approximately 25 structures at the top of the bluff in order to facilitate a cut back to a stable slope of 2H:1V approximately +65 feet MLLW from the bottom of the revetment. A temporary easement at the top of the bluff would be needed for construction of the revetment. It is not anticipated that there would be a significant loss of stone from the structure over the life of the project. It is estimated that approximately 2,900 cubic yards of armor stone would need to be replaced every 20 years. 55